you should have the Bently manual, check Pelicanparts articles too
take your time try not force anything or scratch the sides of OBC with screw driver.
use plastic scraper or painters tape on metal scraper screw driver if needed
try not to drop stuff into the black hole
try not to break bulb or wires, dont get finger prints/ grease etc on new bulb
clean up while you are in there.
make sure you get all the screws back in when putting it back together or the whole thing will wiggle squeak.
Its fun when it works.
set the speed alarm to 156 mph, lol
here it is: Pelican Technical Article: OBC light replacement for the BMW E30 3 Series