Go to Autozone & pick up a new headlight motor for $70. It has a lifetime warranty on it so you can bring it back the next time this happens & they'll exchange it for free (just hold onto your receipt).
For now, you can temporarily fix it by manually turning the motor/gear 180* then reattaching the metal swing arm.
instructions/pictures here:
http://www.bfranker.badz28.com/headl....htm#FreeGuide