Car has been on and off overheating alot the past year or two?

Replacing the sensor will not fix anything. It is just reporting the overheating, not causing it. Much of what you described could be attributed to a leaking cylinder head gasket. Before you keep running in circles and get "wrapped around the axle", have your mechanic perform a chemical test on the head gasket. That involves drawing air from the radiator, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are sneaking into the cooling system, that liquid will turn bright yellow.

That air that can leak into the cooling system can pool under the thermostat. That will cause it to not open and the engine will overheat. Thermostats must be hit with hot liquid to open. Hot air will not do it.

If the test is positive for a leaking head gasket, no other attempts to solve the problem will be successful. The head gasket will have to be replaced and the cylinder head must be checked for pitting to be sure that will not happen again. If there is no indication the head gasket is leaking, we will need to look at some other possible causes for the overheating.