If you don't want to give any power to the mirror, manually tilt the mirror down and towards the car. You'll notice a silver wire clip from the top of the mirror. That holds the mirror in place. Unclip it and fidget with it a little and it should come right off. Worse case scenario, you break the mirror while getting it off, fix the wires and pay $50 for a new one. If you were willing to take it to a mechaninc I think $50 isn't too bad.

Good Luck