What's the best way to replace the Cluster Voltage regulator?

I actually looked over the diagram again and the lights come from the headlight switch, but the gages come from the alternator/battery through fuse 6 (these diagrams are confusing!!). The current does feed through the voltage regulator on the firewall, so if that is bad then it could cause an overcurrent, but it wouldn't fail overnight, I wouldn't think, since it was probably working before.

You could go crazy with this and start by pulling all of the light bulbs to make sure nothing is shorting to ground there. If you lose fuse 6, it traces back to losing power to the whole cluster, I think. Then maybe see if you can disconnect the gages one at a time to eliminate any grounding short there. Also check to make sure none of the harnesses have any connections touching and that all of the circuit boards are insulated (not going to ground). I'd hate for you to go buy a headlight switch and it not be the problem, though it would be nice if it was that simple.