Leaky transmission on a 2000 Mercury Sable

My transmission just started to leak on Saturday. My brother said it was leaking from a rectangular seal that fastens to the car with two plastic screws. The guy at O’Reilly’s said that was just a protective plate to keep rocks from damaging my tranny. He sold me a torque converter seal and stated that is what is leaking. He also mentioned an axle but didn’t go into detail. I need to get this fixed but can’t afford a dealer or independent repair shop. Does anyone out there have a answer as to what part ultimately needs replacing?

Stop by your local library and see if they have a repair manual covering your car.  Read the part about replacing that part.  Do you think you can do the work?  Do you have the tools?  If not have someone do it for you.  In the mean time make sure the transmission fluid is not low or you will be buying an new transmission soon.

My Chilton manual recommends that only transmission specialists repair this transmission. Do not risk damaging your transmission or you’ll be faced with
a huge repair bill. Replacing this seal might not be that expensive; get an estimate.

You really need to get someone to verify exactly where the leak is coming from. If the fluid is leaking past that little plate (which really has nothing to do with sealing anything) then that means the torque converter seal is leaking. The transmission has to come out of the car to replace this seal and it’s a pretty big job.
If you’re not mechanically inclined then this would be out of your league.

An axle seal could also be leaking and allowing the fluid to run down around that plate, which could lead someone to think the torque converter seal is leaking.
Part of the front suspension has to be disassembled and the axle shaft removed to change one of these seals.
Another possibility is a transmission cooler line line leaking and allowing fluid to run down and causing the appearance of a faulty torque converter seal.

Everything is guessing without seeing the car. Everything needs to be examined very closely before worrying about a torque converter seal since it would be unusual for one of them to leak on 2000 model car.