Let me google that for you... ...seriously though, put it in a warm place, pull as many panels off as possible and wait until dry. Then try again. Having said that, by plugging it in, assuming it's still wet in places, you'd expect a short circuit across at least a few points. If you've blown capacitors or burnt out resistors (or both), or worse blown the CPU or another surface-mount component/SMD then without a solder/desolder station, multimeter and some pretty fancy hand tools you're talking an exercise in frustration. If you want to spend 3-4 hours on someone else's workbench tracking down the problem, that's fine, but most people will quote 2-4 hours labour, plus parts for this, and as there is no guarantee that the parts will be available or that it's an economical fix, I understand why most places wouldn't touch this. If you take it into the apple store, explain that it has a defect of technically unknown reason and ask for a service quote, you may have more luck. It's guaranteed to be out of warranty though.
