No the GDC # doesn't change, it will stay through multiple incarcerations or probation terms. I've seen it once in my career and that was because of a name mix up.
I've never been to that TC, but I know some of the ppl that work there. They work at the chicken plant and make good money. I've heard of some guys leaving there with thousands of dollars in their pockets.
Tell him to follow the rules and don't be late coming back in from work and he should do just fine.
I in no way answer for or on behalf of the GDC. I am here to give general information only.
Hopefullly I can help those on the outside, understand what's happening on our side as well as their loved one's side!