Chevy C1500 '89

[911ls]

I can't understand what my son is doing when he takes over the wheels of this truck. Initially, he was complaining about it not driving smoothly; jump from one gear to the next. Later we learned that he was driving it in the 2nd gear. Once that was corrected, and all fluids were topped off, it ran well for 2 days. It began to run hot, smoked, leaked anti-freeze and eventually stopped running. We learned that the water pump needed replacing. We took care of that. He got the truck today and says that it takes a while to go from 1st to 2nd (automatic drive) and the heat doesn't work now. None of the gauges suggest a problem. What could be the cause?