Nate,
That mouse pee is some pretty nasty stuff. I had a mouse condo behind the windshield on my 46. It rusted a pile of parts and worst of all, the inside still stinks like a mouse toilet.
As far as your problem goes, you will probably have to fashion a patch piece. It will take a lot of metal work to do this.
If I were you..I would make a south dakota/Wyoming run... If you have not started yet, keep your eye out for a dry climate cab. Get a couple of buds, a trailer and go for it.
If you can, post pics and you will get some more advice on how/what to do. Either way, it does not sound like an easy fix.
