I'm having a problem with my folding mirrors too. It's only the passenger side having the problem and I thought I'd take the mirror off, replace the gear and reinstall. I hope it's as easy as: folding the mirrors, manually unfolding them and resetting them.
Update: I attempted the reset with no luck. I'll try& take it apart to replace the gear another time. My non-power folding mirror is reinstalled. Fortunately the dealer may replace my dead power folding mirror.