Took it in to change transmission fluid, they

Buy filter and transmission pan gasket, (small bottle of Indian head)..
- unbolt the couple of dozen or so bolts the hold the tranny pan.
- leave about 6 bolts loose (2front, 2 middle, 2back
-get your used oil receptacle ( bigger the better)
- there's about 3qts of ATF on the pan you must drain carefully
- remove the 2 bolts left on the front so that your tilting the pan to drain the ATF
- Remove tranny pan and old gasket
- the fileter is just pressure press( check your shift solenoids for loose ground wires and cracks on the wires(
-remove filter and clean old gasket remains stuck on transmission and tranny pan
- try not gauging the transmission if you used a blade(I used a torch)
- press new filter on the pump pick up hole(reverse of removal)
- used the Indian head gasket shellac to help you keep the new gasket in place(put some of the bolts tru to aid you with lining the gasket
- hand tightened the pan bolts crisscross pattern, make sure it's even when it goes back
- TORQUE to specs, blah blah blah woop ti do, yuz freaking done
- refill the ATF about 3 qts
- let it rest cool down for like a hour, check your atf fluid cold and hot
- Not rocket science ( advisable to change transmission filter every 20k miles or after 4 oil chages) depending on the manufacturer. Good luck...

Transmission fluid should be checked with the engine warmed up and running in Park. The dipstick is always near the back of the engine bay, and is VERY long when you pull it out. Transmission fluid should be red. It should not be brown.
Changing transmission fluid is much more difficult than changing engine oil. Engine oil can be changed by removing a plug and draining it out. Transmission oil can only be changed by removing brackets, removing the pan (think of a shallow oven pan bolted to the bottom of the transmission) and letting all the fluid drain out. A transmission fluid change should ALWAYS include a new filter and gasket as well. This is one best left to a shop with the proper tools.

yes by filling through the transmission dipstick tube, if you have a "fill for life" model without a dipstick tube, you will need to get under the car and on the side of the transmission look for an alen head socket about half way up the side, fill with the correct fluid until the fluid is level with the alan socket you removed, when it starts to flow out ,there is plenty in the transmission, be careful, it has been debated by engineers that a car that has over 100k miles and never has had the fluid replaced should be left alone, as the wearing and viscosity of the fluid will change with new fluid hence the phrase "fill for life " fluid. This fluid is usually recognized as atf+2,3,4.. dexron and mercon are servicable fluids

toyota sienna 2011 model has a sealed transmission that's why you cannot find dipstick. the transmission fluid is rated up 100k miles that you don't need to check the fluid.

Well, you have to put the car up on a lift, clean fluid and find out where it is coming from. If the front pump area seal, yes, you need to pull the trans to fix that. If it is leaking from the pan, that can usually be changed without trans removal.

TRANSMISSION SLIPPING CHECK TRANSMISSION FLUID LEVEL.IF FLUID LEVEL IS OKAY.YOU HAVE 30000 TO 60000 MILES ON VECHICLE YOUR TRANSMISSION FLUID + FILTER CHANGE IS DUE.IF FLUID CHANGE DONT HELP YOU HAVE FAULTY 1 - 2 SHIFT SOLENOID AND TORQUE CONVERTER SOLENOID.YOU COULD HAVE FAULTY TRANSMISSION OIL PUMP AND BROKEN DRIVE CHAIN.

if your talking about the transmission oil pan,it will be black with about 12 bolts holding it up.

Have supplies ready(long stem funnel to reachfill hole, 4 qts honda genuine atf-z1, rags for drips)
1. First, park the car while its hot on a flat surface and turn the engine off. Locate the yellow transmission dipstick and remove it and wipe it clean.
2. Look for the the ATF fill plug and washer(below and to the left of the brake fluid reservoir) 17mm marked "ATF" and remove it.
3. Locate the drain plug(not the one on pointing towards the drivers front tire but its located on on the drivers side of the transmission pointing towards the passengers side and lying horizontally) and remove it along with the washer. Its blue and is a standard 3/8 square drive plug and remove it. Drain completely. (wait 15 min or so until ALL is gone and replace the plug after throughly cleaning the magnet that is attached to it).
5. Replace atf fluid(honda says 3.3 qts- but mine took 3.8 to bring to first hole in dipstick level-check while running(use honda z-1 fluid only-yes- its expensive).
6. Replace fill bolt and washer and tighten.
7. Replace dipstick, let engine get hot and recheck. Recheck again after driving a day or so.
Your done-good work, you saved a $100 dollars...

It can be changed for every 60000 miles..

Fluid - A/T: Service and Repair
Transmission Fluid and Oil Filter Changing
REMOVAL PROCEDURE
1. Raise and suitably support the vehicle. Refer to Vehicle Lift Points.
2. Place drain pan under pan
3. Remove oil pan bolts from front and sides only.
4. Loosen the rear oil pan bolts approximately four turns.
5. Lightly tap the oil pan with a rubber mallet or pry to drain the fluid from main case.
6. Remove the oil pan bolts from rear oil pan and gasket.
7. Remove front oil pan bolts leaving one corner bolt in loosely.
8. Lightly tap oil pan with rubber mallet or pry to drain fluid.
9. Remove the following remaining components:
^ The front oil pan bolts
^ The oil pan
^ The gasket
10. Remove the oil filter bolts and filter.
11. Clean the following components:
^ The transmission case
^ The front adapter case
^ The oil pan gasket surfaces with solvent
^ Air dry
^ All traces of gasket material must be removed
INSTALLATION PROCEDURE
1. Install the gasket.
2. Install the oil filter.
3. Install the bolts.
^ Tighten the transmission oil filter bolts to 20 Nm (15 ft. lbs.).
NOTICE: Refer to Fastener Notice in Service Precautions.
4. Install the front oil pan.
5. Install the front oil pan gasket
6. Install the front oil pan bolts
^ Tighten the front oil pan bolts to 11 Nm (96 inch lbs.).
7. Install the following components:
^ Install the pan
^ Install the gasket
^ Install the bolts
^ Tighten the oil pan bolts to 11 Nm (96 inch lbs.).
8. Refill the transmission with DEXRON III through oil pan fill plug on the side of the (main case) oil pan. Fill the transmission to lower edge of oil
pan fill. Fill plug opening using and oil suction gun.
^ Tighten the oil pan fill plug to 45 Nm (33 ft. lbs.).
9. Lower the vehicle.
10. Check the transmission fluid level. Refer to Transmission Fluid Checking Procedure.

This page explains how to change the transmission fluid but about half way down the page it tells how to check for the proper amount of fluid:
http://www.newbeetle.org/forums/showthread.php?t=1036

There isn't a transmission dipstick for this car.