Had the same problem over winter in mine a few years back. Bastards had shat and pissed everywhere. Built a nest under the back seat and wrecked the fibre trim under the dash. Fortunately no serious damage though.
I stuck a couple of traps down baited with peanut butter. Got 5 of the sods in about 3 days.
after that left bait boxes and traps in the garage in case any more decided to take up residence.
had to take all the carpets out and scrub them to get rid if the smell. Washed the floor with disinfectant as well