yes ive heard it is compatible. this is one mod i was planning on for my 323Ci. The auto dim mirror function I do not know if it will work. If you have auto dim now, it will def work, if you dont, i dunno if your car is prewired for it.
The only thing that is holding me back on doing it now is the price tag at like $300+-
yes, the m3 mirror will fit in perfectly. for the auto dim, do you have the premium package? If so, then the auto dim function will work as well. If not, you may want to ask your dealer about that. i'm not exactly sure if it is pre-wired or not. i would think so.