Don't take the evidence of mice lightly, I did and we paid for it, for two month's this winter we weren't able to run the AC for due to the horrible mouse smell we were left with after I cleaned up 3 dead caught two in the bath one in the furnace/water pump/water heater bulkhead and one decomposing which was on the top of a cabinet in our FW, so high we didn't see it.
I've closed in the back the the stairs with a piece of plywood and caulked it that go to the bed/bathroom. The drawer was wide open to the bulkhead and a highway for mice into the inside of the trailer. I also caulked an opening bringing wires from the exterior of the trailer, under the stair light, into the bulkhead to the rear of the compartment, but I have much work ahead of me. All openings into the frame which allows access to the underbelly and wiring chases need to be sealed along with the hydraulic frame openings used to open and close slides. Somehow I need to seal off any openings around the front leg jacks that lead into the front cap also and the back cap. Access leads to wiring chases and the AC ductwork.