UPDATE: So I didn't drive the car today- I came home and decided to do this myself via the front sump pump. Took all about 15 minutes (jacking up the car took the majority of the time), and everything is back to normal. About 2/3 of a quart came out, and I guess it was enough to put me back into the optimal range. I didn't have a funnel handy so I just cut a water bottle in half and inverted it right into the oil bottle. Worked like a charm. This was definitely a super easy DIY. The full-on oil change is probably just as easy. The only thing I recommend is getting ramps (I didn't have this, so I just used jack stands on either side) and thick latex gloves.
Thanks again to everyone for the replies. I wouldn't mind paying $160 if I had to, but clearly, in this instance, the stealership was trying to rip me a new one.
2011 AW/FR Extended E92 M3... fully loaded