if you didn't get mud in the vehicle you can usually save it by stripping out the interior, using a wet dry vac and getting as much and you can out..
then put some big ass fans in the vehicle to dry it out, and coat everything with this stuff:
it will prevent the wires and connectors from rusting..
the deal is to get on it ASAP, the longer you wait the worse it will be..
it is a lot of work, but we have saved a few cars from the totalling fate this way, we also treat our boats with it because we dunk them in salt water more than fresh water out here.