After looking at it some more tonight, it looks like the kitchen cabinets might be easier to remove than I originally thought. I should only need to remove three pieces of wood to really get full access on the inside: the "L" shaped countertop, and then the two front faces that form the cabinets themselves. If I pull all the various quarter round and 1x1 pieces that hold it all together, it looks like it's largely just stapled in there. Hopefully I can get it out without destroying it, but worst case I'll have to use the old to make templates to make new.
I may still need to pull the exterior apart to fix it properly, but looking at it in more detail there's some definite floor damage under the cabinets I'll need to repair anyways. It doesn't seem to extend inboard very far at least, since the area in front of the cabinets seems very solid. We'll find out... plan on starting inside work on it tomorrow.
This will also allow me to do a better diagnosis without having to "crack open" the outside.