Here's the situation. The previous owner of my home had a cat that used various rooms in my upstairs as a litter box. There are various walls soiled with cat urine. The corners are particularly bad, so bad that as I attempted to cut the drywall out the wall just crumbled away. I thought that maybe just removing and replacing the drywall would suffice but it became apparent that the urine had soaked into the bottom of the studs in some of the corners. And the board that the studs sit on top of (is this called a sole plate?) also has some urine soaked in. The urine didn't appear to have soaked too far into the boards. There is also insulation that will need to be replaced in these corners. As it stands now, I have cut 4 feet of drywall from the bottom of the wall. My questions are - do the entire bottom sections of these corner studs need complete replacement and if so, would I be better off calling up a professional? Could I get away with sanding away an 1/8'' to a 1/4'' (estimated deepness of cat urine) of the studs and sole plate without compromising the structural integrity? Thanks.