moabjunkie

My 1990 Legacy just started overheating. I got the car as a gift a few weeks ago, so I don't know much history on it. When I noticed the temperature gauge rising, I instinctively turned the heat on full blast. But, only cold air came through. I understand there are a few things I need to check... 1) Heater Control Valve is stuck. I'm not sure where this is. Can anyone help me locate it? 2) Replace the thermostat - always a good place to start. 3) Radiator clogged 4) Heater core clogged Can anyone offer some advice on where to start, what to knock of first, etc. THANKS!