Gas guage inop....

Hi, just bought a 96 Jetta GL 2.0. The person I bought it from said the gas guage stopped working (inaccurate)
On a full tank, it read half...any ideas? Sender, grounds?

First option, go to a salvage yard and get a new sending unit. Second option, remove your sending unit and check the reisistance across the sensor wires with an ohm meter with the float fully up and down then ask a dealer or professional mechanice what the measurements should be. I had the same problem and it was caused by varnish (gum, whatever...) from the gas that had built up a film. After cleaning it, it worked fine.