If you're under warranty and want to go to a dealer ship try Ted Eibach at Sterling BMW. Ted has always taken care of me with any issue.
Don't go to the dealer for an oil change, they charge too much.
Mach V has good mechannics and are located in Sterling, Va.
Funktion Auto is also very good and in the Dulles area.
I do most of my work/mods, but those are the experiences I can personally speak of.
G5 ISO|BMS Flash|CP-e|ETS|ER|Forge DVs|KW V1|M3 Sways|BBS CH|BMS|