With proper treatment and medication can someone still live a full life even if their HIV has progressed into AIDS by the time of diagnosis?

Absolutely. Thousands of people in the US alone are living proof, John. Why do you ask? I think perhaps it's time to be brave, sit down with a decent and humane physician, and accept his/her friendship and caring, even if it's perhaps been hard for you to accept warmth in the past. Whatever happens, you'll be nurtured through this experience and come out a happier and more fulfilled man.