Are you sure your gauge is the culprit here? Those in-tank sending units are also likely to fail, and a bad ground or connection could be to blame. But it's easy to check:
In the engine compartment on the firewall, there's a 3 way connector [C502] for the fuel pump and fuel gauge. Short the fuel gauge pin and the ground pin (make sure you don't ground the fuel pump pin! Use a fused jumper!). Now connect a 90 Ohm resistor (22+68 in series) to those two pins. The Gauge should read E, then F (or was it vice versa?). Allow for 1 minute for the gauge to settle. If it doesn't reach F or E, repeat the test on the back of the I.P. panel (the contacts are visible once you take the I.P. cluster apart.). Repeat the test. If it works now, you have either a bad connector or cable or a bad ground. If it still doesn't, it probably is the gauge.
From: Oliver Scholz
Be sure to check out Oliver's build-it-yourself gauge tester on his web page.