How do I get papers to have my deceased sons last paycheck from his work? And how much will it cost?

I have lived with my son the last 4 years. He's been separated from his wife for 6 years but never got legally divorced. My son passed away in a wreck in March of this year. He has a final paycheck that is due to him. Since his death, his ex-wife has remarried and does not have any interest in anything my son had. I am now taking care of his mobile home and his dog and in contact with his former boss. I do not want to get him into any legal trouble so I am just wanting to know what I need to do to get the final paycheck to help settle some of my son's debts that he left behind. If the cost is more than paying off his debts then I will not waste my time in pursuing this matter. Please help me.