89 928 S4 transmission leaks

I've been restoring this car for about 5 years now so it sits, last year I took it out of the garage and put it in the driveway for the winter. All the transmission fluid in the reservoir leaked out, found the nut was loose, tightened it, filled it and all was good with the operation of the transmission, it leaked again so I took it to my mechanic and he replaced the o-ring and filled it. When I went to pick it up I looked underneath and it was leaking again, he said the reservoir is known for cracking so take it home I'll order one. Car ran fine all the way home (20mins). During the few weeks it leaked a lot, I put a boot mat under it to catch the fluid and it filled the mat...but!....the reservoir is still full and it does absolutely nothing when I put it in gear, the screws of the oil pan are dripping and it will not accept fluid from the reservoir, I towed it back to my mechanic and he says that it needs 2 sealing rings, a drive bearing with re/re $5500.00 cdn.
What does a couple of seals and a drive bearing have to do with the transmission not taking fluid from the reservoir? before all this the transmission shifted perfectly.

Hi, I am not sure about the drive bearing, however I would like to think that at cold, starting the car, running through the gear selector, waiting up to 5 or 10 seconds before each shift and then checking the fluid level, if it has moved down to the 20 degree mark (see picture showing reservoir), there should be no problem with fluid going into your transmission and torque converter.

I had a lot of issues with transmission leaks. Mine were related to the O ring at the B2 Servo Cover (see picture pointing to B2 Servo Cover), not to difficult to replace, the breather pipe (connection from the top of the reservoir to the transmission body (Porsche Part Number 999 181 167 50), the wrong pan gasket, garage put in part number 126 271 10 80, which was the old type and when I replaced with 126 271 11 80, I had no leaks from the pan. The final leak, was an odd one, it was the reservoir red cap. It turns out the the cap is designed to be torqued down, mine was just finger tight when I got it back from the garage.