Get a trans pan gasket, filter, and fluid at your auto parts store. Drive the car until the trans. fluid is hot (about 5 minutes) then put the car up on jackstands/blocks or a lift. I recommend setting the key to Lock and removing the negative battery terminal so you don't accidentally set off the airbag. Being careful of the hot exhaust, loosen (but do not remove yet) all the transmission pan bolts. When they're all loosened, take out all but the 4 corner bolts. Now ya gotta be careful removing the bolts on the end of the pan because it's 350 degree fluid--you really don't want to spill that on yourself. However the old gasket is likely to stick. Take out the corner bolts from one end, and hopefully you can tip the pan down in a controlled manner, spilling most of the fluid into an appropriate container (depending on model you may have up to 6 quarts). If the pan sticks, you can whack it with a rubber mallet or pry with a screwdriver, but be very careful not to damage the mating surfaces or it will leak. Now the filter should be easily visible, replace that. Carefully clean the transmission pan, and line up the gasket. Make sure all of the bolts go through the gasket before you tighten anything. Tighten those bolts in stages, in a crisscross pattern--first to finger-tight, then to moderately tight, then torque to spec. Fill the trans through the dipstick hole. Go slow and don't overfill.