I need to know what star wrench i need to remove the brake calipers

Probably is a T-50 bit that fits on your rachet...you can buy a set of star key bits...these are not allen wrenches...Hope this helps.

you mean brake rotor? depends what kind of car or truck. most have disc brakes and have a bracket that holds the caliper. that has 2 bolts on the back that would need to be removed and then the rotor can be removed. you will need some special tools to remove the caliper. some have bolts, alan wrench or star socket. depends again what kind of car.

If its the cylinder for the rear drum brakes and not the caliper bolt it is a e6 female torx socket or wrench that will remove the two retaining bolts.

First, you you managed to give the year, but you forgot to mention MAKE and MODEL...Nice-to-know ...especially since you are asking for SPECIFIC information that does not apply to all vehicles.
Second, I have no idea what a "star" tool is unless you are refering to a "Torx" driver.
Third, MOST GM vehicles built in this century require neither an Allen wrench or a Torx driver. Most calipers can be removed with either a 15mm or a 13mm socket or wrench.
I would recommend removing the tire and wheel assembly to LOOK at the caliper and see what is holding it.

You need two special tools 1. A T60 torx bit to remove the caliper bolts 2. A caliper piston compressor two large c-clamps will work but compress evenly and SLOW

Things You'll Need:

• New brake pads
• C-clamp
• Allen head, star head, or 6-point socket wrench
• Lug nut wrench
• Brake fluid

Remove the old Brake Pads
1. Step 1 Park your car on a level surface. If you have a stick shift car, make sure the car is in gear. Place blocks in front of the front tires so the car does not move while you are working on it.
   
2. Step 2 Open the hood of your car. Locate the master cylinder and brake fluid container. If necessary, remove brake fluid until the level in the container is less than half full. A turkey baster is a good tool for this. Put the brake fluid in the plastic container and dispose of it the way you dispose of motor oil.
   
3. Step 3 Raise the rear end of your car with your car jack. Remove the rear tire or wheel assembly.
   
4. Step 4 Use the socket wrench to remove the lower caliper bolt from the back of the caliper. Rotate the caliper up.
   
5. Step 5 Remove the brake pads from the caliper.
   
Install the new Brake Pads
6. Step 1 Insert the pads into the caliper.
   
7. Step 2 Place a large C-clamp on the body of the caliper and slowly tighten the clamp evenly. Compress the piston until it is flush with the caliper.
   
8. Step 3 Lower the caliper and use the socket wrench to attach the lower caliper bolt. Tighten the bolt to 16 to 24 ft. lbs. (22 to 32 Nm).
   
9. Step 4 Replace the tire wheel assembly tire. Lower the car to the ground. Pump the brake pedal a few times to seat the brake pads.
   
10. Step 5 Add fluid to the master cylinder container to replace any you removed before you removed the old brake pads.
    
11. Step 6 Season the brake pads by making only gentle stops when you are driving for the first week after you install the new brake pads. Try not to do any hard stopping when you are seasoning the brakes.
    

You'll need a T-55 torx bit to remove the rear caliper pins/bolts. You can try using an insert style bit...one that removes from the socket or perhaps purchase a replacement bit (one that would be used in a cordless drill/driver.) The one I used had a 5/16" hex shank. Like you said, there is very little clearance between the head and the leaf springs, which won't allow room for a breaker bar and torx bit. So using a 5/16" wrench, ( I'd recommend a 6 point box wrench to prevent slipping or rounding off.) I was able to loosen the bolt. Or plan B is to remove the caliper mounting bracket which is held on by two 21 or 22 mm hex head bolts. Which would have to be removed to remove the brake rotor.

you have to remove the the wheel of course and take 2 bolts out of the back of the calipers, one top and one bottom. once they are out you should be able to take it off of the rotor and just remove the brake line and e-brake and then put in the new ones in reverse order. you will have to adjust the e-bake after doing this im sure so figure out how to go about that first.

If you are just removing and replacing the pads, you will need, i believe a 13mm wrench, a screw driver (flat head) and a "turn in caliper compression tool" because your rear calipers also act as your emergency brake when it's engaged. You will see 2 divits across from eachother on your caliper piston. Once you have the tool inplace and the slots lined up with the tool, turn clockwise and turn the caliper piston in. If it will not turn, then it's defective and will need to be replaced before you can install the new pads. If you need a turn in caliper tool, you can rent one at any autozone or advance auto, pay for it up front and get a complete refund when you are done and bring it back.
Good luck!

So this is what it takes to replace rear brake rotors on a 2003 Mercedes E320;
1) open the bonnet (hood) of the car and loosen/remove the cap off of the brake fluid resevior.
2) remove outer spring clamp from brake assembly (it clips in to the iner edge of the holes of the caliper).
3)using a 7 MM allen wrench, remove the brake caliper.
4) using 18 MM box wrench, remove the caliper housing assembly off of the wheel hub.
5) using a star wrench, unscrew the rotor locking screw from the rotor
6) squirt some liquid wrench on the rotor hub and knock the rotor with a hammer to work the liquid wrench in.
7) using the same hammer, knock the rotor off the hub.
8) using a metal file, lightly file old residue off of the hub and place the new rotor on the hub.
9) set the hub by screwing in the lug nuts and then screw in the hub locking screw using the star wrench, then remove the lug nuts.
10) reinstall the caliper housing assembly onto the wheel hub using the 18 MM box wrench.
11) push back the brake claiper piston to its home position and install the inner brake pad (the one with the snap clips)
12) insert the outer brake pad in the claper housing assembly.
13) slide on the caliper housing with the inner brake pad in place (over the outer brake pad) and screw in the caliper screw rods using the 7 MM allen wrench
14) on the right wheel brakes, DO NOT FORGET to slide in the brake sensor (the one with the black connector) and connect it to the connector on the caliper housing.
15) be sure to reinsert the spring clamp onto the outer brake assembly to set the assembly squarely onto the wheel (there should be no wiggle in the brake assembly after the spring clamps are installed).
16) finally mount the wheels.
17) you can bleed the brakes at this point to release any trapped air (which is unlikely) but be sure to pump the brakes after starting the car BUT BEFORE MOVING IT to re-preassurize the brake system before driving the car.
17) ONE WEEK LATER - recheck brake assembly to ensure all is okay and brake fluid.

This proposed solution is for a 2003 Mercedes Benz E320 and NOT a 2005 model as stated by the limited option selection provided by FIXYA.com when initially describing the problem.