BMW Repair: alternator - transmission, bmw 525i, transmission issues

Question
My BMW 525i 1992 car was dying after several miles at
red lights. battery dead.

Mechanic changed alternator. Now my transmission
won't go into drive. Reverse is fine.

HELP !

Answer
Paul,
 Unfortunately your car has the M50 engine and transmission which I know little about.  If you had an older 5-series that shared the same engine/transmission as the 3-series, I could possibly help.  

 Sounds like you have transmission issues, especially if you cannot physically put the transmission into drive.  Check the knob and make sure that the button will depress all the way, this can hender certain gears if it's not working correctly.

 I would suggest letting a TRUSTED mechanic look at the car, as there are too many possibilities for me to make an accurate prediction.

 Hope this helps,
 Josh