OBC, remove and install.

Open glove compartment and remove pins from restraining straps.
Allow glove compartment to rest on floor.
Remove the two Phillips screws (upper green arrows) and two 1/4 turn clips (lower green arrows). Remove upper cover. Do not loosen striker screws (red arrows).
Disconnect wiring to glove compartment light Remove screws from glove compartment striker plate (red arrows above), remove plate.
Remove plastic trim to left of glove compartment.
Requires BMW special tool number 82 11 1 466 971
Use flat end of tool to open left and right screw covers
Loosen screws until they stop turning
Gently grab radio at cassette door and slide out of opening. Gently place radio on center console, there is no need to disconnect wiring to radio.
Remove the 4 screws securing the OBC unit to the back of the dash plate.
Pull unit out through glove compartment and disconnect wiring.
If OBC back-lighting is out, there is no need to remove the unit. Check this tech tip.
Installation:
If unit is being replaced, swap coding plug from top rear of old unit into new unit.

E30 M3 Repair Manual V2.7. Copyright Š1999-2001 Koala Motorsport & Brett Anderson