..HELLO! The engine you have and that year have been very problematic with blowing head gaskets that allows exhaust into the cooling system. You can try replacing the thermostat on the top of the manifold but don't expect a real change afterwards. With your symptoms I have to really expect you to find one or both head gaskets blown. An auto repair shop is best equipped to diagnose this.
The coolant runs from the engine to the radiator top hose.If you get air(exhaust) introduced into the system it goes to the top of the manifold as steam. T-stats won't open with steam causing the overheating--no heater temp. and cool radiator that you describe.due to no circulation. Expect a $1500.00 repair bill from a shop to replace both gaskets.
I hope this answers your question.