Open it up, and put it near a heater and/or a lamp. If there is anything that can store water than see if you can open it a crack. Then leave for quite a few hours. Perhaps use hair dryer on it. Once lots of hours has gone by then try booting it. If fails then buy each component again one at a time until it works (taking component back if fails). If suspect multiple component failure then buy all the bits again and keep replacing with the old ones one at a time until it works again. Then do a bit of mucking around to see what is still working and send the parts that don't need replacing back again. Annoying, but possible.
Hopefully drying out is all thats needed. I watched a gadget program the other day where a bloke jumped into a swimming pool with a bunch of gadgets then cracked them open (where possible) a little, and put them next to lamps and heaters for like a day. After that most of the gadgets worked again. If you are slightly wrong though and try the gadgets before totally dry then can fry the circuits, which may have happened to you. But hopefully only one or two peripherals are toast.
Cheers
I am 99% probably lying in bed right now... so don't blame me for crappy typing
