Now that i have all of your posts in front of me, it seems coolant loss is the primary problem. NOT overheating?

I'm not sure how mechanically inclined you are, so i'll start simple, you already said your taking it in.

How much or how fast are you losing coolant?

Is there a puddle under the car? Does it form under that radiator or the engine? if its under the engine it could be the water pump, or head gasket, or heater lines etc.. depending on other factors like do the belts look wet? is the block wet? any pockets in the casting filled with coolant?

If there is no puddle under the car, does the exhaust puff smoke on start up?

Is the passenger floor wet, interior smelling musty, or strange coating on the windshield?

Is the oil still oil? if it is mixing with coolant it will smell, look funny and can be sort of frothy..