Screwed up simple oil change.
Overfilled crankcase by at least a quart, and over-torqued the drain plug (which Chevy purposely designed with a 10 mm head to keep the service people from wrecking the oil pan -- a much more expensive repair).
I needed to drain out the extra quart, as well as replace the drain plug.
It appears that a service visit here guarantees a second, as they need to fix what the broke the first time.