I'm inclined to DIY whenever possible and convenient, including shocks, brakes, and fluids. you can also read codes off your car, research the code, and then decide if you're comfortable doing the fix.
iIf you'd rather not DIY, it stands to reason that many tasks shown in the DIY forum could be performed by any non dealer competent mechanic. Just make sure they use BMW approved fluids and are familiar with proprietary methods. If not sure, try a shop that specializes in BMW.
AA Stage 2 - M3 control Arms FR - BMW PS2 - Dinan springs - APEX EC-7 - H&R front swaybar - GC street camber plates - Whiteline subframe inserts