1992 Plymouth Voyager been running hot

1992 Plymouth Voyager mileage: 164,000. Hey guys, need your help. I have been stiffed for $500.00 bucks. The engine has been running hot; temperature gauge on hot, blowing cool air. First it was "running low on oil; tightened timing belt. Week later same problem: then my so-called mechanic installed a thermostat. Couple of days later; same problem: this time "needed" a new radiator cause it was leaking antifreeze. Two days later same problem. This time they want to stiff me for 350.00 for a "head gasket”, Can't anyone, tell me what is wrong with it? Need a second opinion. HELP!