You should be OK... OBC memory will be lost (no different that resetting the mpg, avg speed and trip ODO), but otherwise no problems. You'll have to reset the clock too...
I've disconnected the battery in both the E46 and the E39 many times with no issues, and did a battery swap in the MINI myself. A battery swap isn't any different that disconnecting and reconnecting the existing battery...
__________________
ZBB
|