Q: We changed the temperature sensor because we broke it and now the check gauges light won't quit flashing, and the temperature gauge jumps to high

We have been changing little stuff, here and there makin new. We have recently changed oil, front brakes, plugs, wires, thermostat, waterpump and temp sensor(cuz my husband broke the wire while trying to fix another issue.) Now the truck temp gauge runs as high as possible and the check gauge's light flashes? We have since rereplaced the thermostat. What could cause that? We had a different prob before overheating issues started. After truck gets hot it tries to die at red lights or stop signs but runs fine when restarted. So we think we may have figured that issue out (we will know this afternoon when we are able to test after work)but now we are havin this secondary issue? Any ideas? Is it common to get a bad temp sensor? Or could something else all together be the issue? We are trying to make this truck safe for our teenage son, please help if you can.
My car has an automatic transmission.