Since the spoiler went up on its own when you left the dealer, it seems like the circuit was OK at that point. I am guessing that the fuse blew when you tried to retract the spoiler. Maybe something stuck in the mechanism causing the motor to overheat and blow the fuse. You could try disconnecting the spoiler motor, replace the fuse, and see if everything else works. If everything else is ok, it has something to do with the spoiler mechanism.