Woo hoo - thanks to Greg, I fixed this thing myself this afternoon.
Guys - assuming you're in a late 90's F-150, you can avoid any cosmetic damage to your headlight switch assembly by using the directions in the Haynes manual to remove it. It's designed to just come out without any prying.
Turn the knob to the ON position and then pull it out just a bit. Look for a hole in the bottom of the knob. Use a tiny screwdriver and push in that hole to release the knob.
After removing the knob, turn it 180 degrees from its original orientation and put it back on (in other words, put it back on backward). Turn it counter-clockwise two notches to the OFF position, and then turn it
clockwise until the entire assembly releases itself from the dashboard. It took me three or four tries, but once it works it's MAGICAL.
Re-assembly is the reverse.