We took the range hood down. This involved some Interweb-searching for what we expected to find back there, electrically. Luckily, it was pretty straightforward. We flipped breakers until we found the one to the hood, and then it was just a matter of unscrewing various parts of the hood until we found the panel covering the incoming wiring.
We were a bit nervous to see that there was no wall at all behind it, though. What about behind the cabinets themselves?