William,
A defective fuel gauge is normally a fairly straight forward repair if you spend a little time diagnosing the issue before you start throwing parts at it. The resistance in the tank unit increases as the fuel level increases. So, for a fuel gauge that pegs full, you check for power at the tank unit, if there is power at the dash gauge but not the tank unit, you have an open circuit. If you have an open circuit, you can look for the open (probably a green and fuzzy terminal at one of the connectors in the LF electrical bay), or just run another wire.
Gerald