'85 325 e auto transmission problem

I have an 85 325e. The auto transmission only works in reverse. Service tech wanted $2,100 to rebuild it. How hard would it be to pull the trans myself and rebuild it? I have never worked on a BMW before. I am a pretty good weekend mechanic as long as I have good instructions. I don't want to get rid of the car, it has been garage kept since '85. No wrecks, perfect interior, 130,000 miles all routine service has been performed.

i am a weekend mechanic myself and i would never feel comfortable repairing a tranny. from what i understand trannys are very hard to work with, so i have never worked up the ambition to work on them. . .

It is a big job mate, you'll need a good workshop to have any sort of chance. Nuff respect if you pull it off though.