First off make the request in writing (if you haven't already), employment is regulated by the state so laws differ from place to place but typically you need something in writing before much can be done. After that you can either get a lawyer or you can go through the state's department of labor and they will have a specific form (wage claim or similarly titled) for you to file with them and they will take care of things from there, a lawyer will be faster but they are generally not cheap. All of the info that you should need can be found at
http://www.dws.state.nm.us/, I hope that helps.