Ruck gets hot it like wants to lose power?

If you mean the truck overheats because the thermostat is not opening then you need to get it replaced before it does more damage. Overheating can easily cause blown head gaskets and cylinder head damage.

The temperature gauge not working could simply be the sending unit for it. When you drain the coolant to change the thermostat you could change it out and see if it comes back to life.
You do not need to drain all the coolant, just down below the upper radiator hose. The temperature sensor and thermostat are next to each other on the intake. Then refill the system and see if it now works.

One thing you did not mention is how fast it gets hot? Or if it pushes out coolant soon after starting, those could indicate a possible head gasket issue.