The mechanic says my brake fluid is contaiminated at 52,000... does it need rep[lace?

Possible wiring issue to the valve body solenoids or a mechanical issue in the valve.

release the parking brakes ?

The most common cause of your heating problem is low coolant levels. Top it up and keep an eye on it for a few days, topping it up again as needed.
Your brake problem sounds to me like warped rotors. As they turn they will push back on the brake pedal. You will have to get them "turned" on a lathe or rep[lace them. The price is similar, so your choice. Hope this helps.

Then you likely need to rep[lace the fuel pump, check the pressure at the test port on the top of the engine. If the pump is the problem you must drop the fuel tank to access it. Also change the filter if a new pump is needed.

LOOK ON ALL YOUR WHEELS TO SEE IF THEY ARE WET FROM OIL THAT IS THE PROBLEM TELL YOU MECHANIC YOUR LEAKING BRAKE FLUID FORM WHICH EVER BRAKE CALIPER OR WHEEL

the problem to start with is a bad brake master cylinder and will remain so until the master cylinder is replaced
brake systems operate front left back right on one section of the m/cyl and front right back left on the other section
take it to a professional brake shop and have the job done safely

Sounds like it may be a defective brake fluid level sensor on the master cylinder.

Hello David, you received very good advise from the last person that contacted you. If I were the one to start looking for the problem, it would have been in the area of the brake booster hose that goes from the brake booster to the engine. I strongly believe you have a bad vacuum leak. Check this hose for cracks in hose or at ends and replace. Your problem should go away and your engine will run better. Please let me know how you make out. GOOD LUCK.

Connected to your brake pedal is a switch. When you mash the brake pedal down, it actuates a solenoid in shifter that allows you to put the car in gear. If that solenoid is going bad or the mechanisms in side the shifter are bad, then that will prevent you from being able to put it in drive.

yes they do need replacing.