Already legally married, but having a wedding which my uncle will officiate at...QUESTIONS!?

Anyone can perform a ceremony. Its only a few people that can make the ceremony LEGAL. If you weren't already married, he would have to be licensed int he state the ceremony is performed in. If not he/she couldn't say you were legally married. But in your case...you are fine. How nice it is to have a family member make the renewal or re-commitment official. :)