engine overheat and cold air: thermostat?

I would check the cooling system to see if it was low on coolant first. This would cause both the overheat and no heat condition. If low, fill cooloing system to proper level and check for proper operation and heat. If that solves your problem find and repair the leak in your cooling system. If it still overheats and you have no heat replace the thermostat and flush the cooling system and refill with the proper antifreeze ratio.

The thermostat replacement is an easy do it yourself repair. You should be able to replace the thermostat and flush the cooling system in about one hour or so.

If you still have problems after that I would suspect a blocked radiator or bad head gasket for the overheating. For the no heat problem I would suspect a plugged heater core or failed valve in the water hose going into the heater core. I would recommend that when you flush the cooling systen you also flush the heater core. To flush the heater core remove the hoses going to the heater core and run water through the heater core with a garden hose. Make sure you run the water through both pipes on the heater core, you will be able to see any crud that comes out, flush until water comes out clean.

All was fine in that same morning, over the past few days, I have been noticing varying lengths of time for the heat to kick in, sometimes works well, other times, not so good. The temp guage has been also been rising to just below the red and then it drops dramatically to well below the normal mark. Have not paid attn to where it leveled off.

I assumed that it was the thermostat that was sticking and that was my explanation.

head gasket sounds expensive. I will start with the thermostat and rad flush. Any other advice to rule out the head gasket would be greatly appreciated. Some say to run the engine and tab on the thermostat housing.

When you change the thermostat as Mike suggested, also change the radiator cap. It's a two way valve and it can wear to the point it will stick, the springs will get weak, gaskets get cracked and etc. It's a cheap item that gets overlooked a lot when having cooling problems. Be careful and don't drive it if the temp goes to red, if the head or head gasket isn't bad it will be if you drive it hot. When you change the thermostat make sure the hose where connected to radiator is higher than the connection at the engine, fill rad and overflow tank to cold mark, run engine with cap off until it gets hot enough to start flowing coolant. Shut off, install rad cap and let it cool down, this should make sure you don't get any air pockets in rad. HTH, Dave