As always, ask around among BMW owners in your area so you can locate a good, honest independent BMW mechanic whom you can hire to do a thorough PPI.
You didn't mention where you are, but if you're in the U.S., you can check with BMWCCA members/officers in your area here:
https://www.bmwcca.org/chapterfinder
You can also go here...
http://forums.bimmerforums.com/forum/forumdisplay.php?237-1976-1989-%28E24%29
...and start a thread introducing yourself and title it "Does anyone here live in or near _____________?" followed up by your intro with "Who can recommend a good, honest indy for an E24 in my area?" in the body of the thread.