It depends on the Parish. I know in Bossier Parish it's like $70 while in Orleans it's like $500 so it varies. Call the Parish Clerk of Courts and ask them. I'd like to send you a link in a message to a Facebook group that may be able to help you.
The process is, you petition the DA for a name change (basically suing the DA). This forces the DA to find a good reason NOT to let that happen (such as felonies or tax evasion). If there's no reason to prevent the name change, the DA submits to the judge that they won't contest the decision. Then it's up to the judge to decide whether they want to sign off on it or not. If so, they send a notarized court order for a name change, which you use to change your birth certificate in whatever state you were born. When you get your new birth certificate, you take it to the DMV and they give you your new license with your new name on it.
