[abaird]

How many miles? GM is notorious for fuel pump problems and installing a pump on a burb might not be cheap. Also, these years of GM's had issues with fuel pressure regulators. That would usually cause an intermittent hard start problem. Hard to tell with the gauge fluctuation though. Maybe a bad sending unit. If you are really interested though maybe see if you can have it for a few hours and have a shop diagnose the problem. You will have to pay for that but many times driveability issues aren't that bad.