Also Check the radiator work mangled cooling fins, more than half can cause a problem. Do a radiator flush, if the guy never changed the oil, I doubt he did a flush.
I second the notion of a good radiator flush. Go to the parts store and get the prestone kit that puts a T in the heater line. That allows you to properly flush the system and eliminate any air trapped in there. Its a cheap troubleshoot and damn good maintenance.
