As long as you can do a COMPLETE inspection, including under the dash and behind all panels, mice damage is no big deal. It is nothing like flood damage where you have the lasting corrosive effects of the water, especially if it is salt water. Mice damage is like a broken wire. Once properly repaired or replaced, it will not come back to haunt you later. I would certainly use all of those issues during a hard negotiation. Since the dealer already knows about the mice damage, you have the upper hand. Just be ready to walk if you do not get a deal that you can live with.
An extended warranty on a coach that old will be expensive and have many many exclusions. The most important is that they will probably not cover gaskets and seals which are most likely to fail at this age. In other words, they will not pay to repair a transmission if it was caused by a leaking seal that drain the fluid while you were on the highway.
I do agree that there are other coaches out there but as with any USED vehicle, there is always a chance of hidden damage popping up. Not too many dealers will allow you to pull panels on every coach to search for rodent damage. You have to take your chances with every RV, even a new one.
