I am a mechanic trying to get the money that is owed to me
A repair shop has a right to a lien on cars that it repairs, as long as the shop possesses the vehicle. Provided that the shop complies with the provisions of Texas Property Code Chapter 70, the shop could secure the right to sell the vehicle. The shop would also have rights under Texas Business & Commerce Code sections 9.609, et seq. The process to perfect the right to sell the vehicle requires the the shop provide notice by certified mail to the persons with an interest in the vehicle (typically, the titled owner and lender of record).
You can review to Chapter 70 at the following link:
So, hang onto the vehicle, and consider pursuing the sales procedure in Chapter 70, or filing suit in small claims court.