snap traps, then toss carpet because you'll never get the mouse piss smell out.
pull stuff and look for the nest. i have a mouse nest in the glove box of the 3500hd i bought. i kicked one out the door and stomped another when i was moving it and a pair popped out from under the rubber floor. my other truck had a mouse nest on the heater box behind the glove box liner, and in the avalanche a mouse built a nest inside the heater duct.