| The switch is fixed!
So, the spring arm actuates a doorbell style button (momentary switch?). That button had become stuck in the "in" position. A little cleaning, a little wiggling with some needle nose pliers, and the button started moving in and out. Of course, pushing it all the way in would get it stuck again. A little more cleaning, a little more wiggling... oh crap! where'd the button go? The button was a white post surrounded by a red rubber whatchamacallit. So, I fished around with the needle nose pliers and was able to find the post again and pull it back through the hole in the rubber doo-dad. Then, it started working right. Push the arm all the way down, the button goes in. Let go of the arm, the button pops back out. With a satisfying "click" coming from inside the plastic body of the switch.
Popped the switch back in the car, reconnected the wires. Hood open = light on. Hood closed = light off.
Who knows how long it will continue to work for, though.
I'm still slightly puzzled that hood closed = button pressed in = no light. But button stuck in also = light. | 
