From what I have found, Louisiana will automatically restore a felony offender's gun rights ten years from the completion of his felony sentence. I don't know when your fiance's sentence concluded, but ten years from there, he would get his state gun rights back.
Of course, the Feds won't automatically restore him and without Federal firearms rights, even once Louisiana gives him his gun rights back, the Federal government can still charge with being a felon in possession of a firearm, if he is found in possession of a firearm. The lead case in this area is United States v. DuPaquier.
So for Federal purposes, he would need to get an expungement if he is eligible for one or apply to the governor of the state for a Pardon.
He can get yourself an expungement without a lawyer if he is comfortable with do it yourself lawyering. Otherwise, there are lawyers who specialize in Pardons, expungements an the restoration of rights.
To expunge a felony, he must file a motion in the District court in the parish where his case was. In the motion, he would ask for a hearing so that he could argue for the expungement. The DA and the police need to get copies of the motion. The forms are on the web for East Baton Rouge parish. He can ask the clerk of the court where his case was, and he would probably have a template.
To apply for a pardon you don't need a lawyer either. You can download the form and read more about it here on the Louisiana Department of Public Safety and Corrections webste. Scroll way down on that page for the link to the application:
Happy holidays and good luck!