As common as the fuel gauge is (assuming non-tach cluster) I'd probably get a few used spares .
Looks like fix-a-gage is for applications where it's stuck at 1/4 tank. While that is one thing I never tried for a fix on my fuel gauge that bounced, I'm going to state that the problem is internal of the gauge, not the resistor on the back, since fluid level is accurately relayed to the gauge (or it wouldn't register the fuel slosh) but the gauge is interpreting the signal real-time, instead of "damped" like normal.