If you have insurance you could try to make a claim if it covers accidental damage. They may or may not honor it - they will almost certainly drop your coverage if they pay out the claim.
It would probably be worth a trip to Canon to see if they can repair the damaged areas if the WD-40 has only affected the top switches and not the major electrical components of the camera.
This is pretty much everything I was going to say. My insurance policy is a rider on my homeowner's specifically for camera equipment and it covers accidental damage and has a $500 deductible.
My first step would be to pack it all up and send it to Canon - the experts in these things - along with a letter explaining what you did. It may be that they can replace all of the effected parts for less than buying a new camera, or they may offer to replace it with a refurb at a highly discounted rate.
After that, depending on how much they said it would be, I would turn it into my insurance company and hope that they pay the claim. And I wouldn't have any problem stating that "dropped in the mud" was the reason for the damage because had it not been in the mud, the WD-40 wouldn't have happened. They weren't properly usable after the mudbath.