Is there anything that can be done legally about this?

My father in law worked with his brother in law in contruction for over five months and this person never paid him a dime, he owes over 8,000 to my father in law. Neverless before all this happened he took my father in law to a car dealer asking him to be a witness and sign some papers on a new car he was going to get so my father in law did, now almost four months later the car got repo and my father in law just found out he wasn't just a witness on the car lease, he is the primary signer which means he is responsable for all the payments on the car. Let me mention that all this happened because my father in law doesn't speak the language clearly and he trusted this person because he is married to his sister and never thought he would do something like this to him. What can my father in law do, can he start some legal actions against this person?