Have you checked all of your ground straps? we have several and if the wires are corroded or anthing that could be your prob. when my last dawgs switch went it just wouldnt do anthing when you turned it but all the lights worked just nothing that wasnt off constant power
just something to check. my dads headlights quit working in his saturn and couldnt figure out what it was. turned out the fillament had broke and fell onto the lower terminals creating a constant surge of power and fryin shit. it was crazy but a possibility in your case.
the thing that sucks is its goin to be something completely stupid that we should have seen or thought about and we are all goin to feel like dumbasses once the shop figures it out. i hate that shit for you man.