Look for bare wiring. What a pain.
Once had a family take up residence in an outboard motor.
I guess the air intakes made for a cozy mouse house.
Anyways, the chewed the insulation off the wiring and made a huge mess.
Another time they nested in a leather seat, and tore it to shreds.
Bits of peanut butter cups are the best mouse bait.
Better than plain peanut butter.
I have had good luck with traditional wooden spring traps, and also with the new plastic ones, which are much easier to operate.
Should wear a HEPA respirator when cleaning up mouse debris, or use 'wet' methods. Wet methods not always practical in and around cars. For dry removal, a HEPA vacuum is probably the way to go. Read more at the CDC: