Thanks for the tips. I did the repair yesterday and sure enough, it was just that single volume control that was causing both sides to fail. I had to loosen the cover behind the wheel to get to the wires initially by taking out the two torx screws. The wires were wrapped around an edge that was making them so short that I couldn't even pull the volume control far enough out to see the wires. After I pryed the wire bundled off of that edge, it gave an extra 3 inches or so to work with and that was all I needed.
