It was the sending unit. I unplugged the sensor an turned the key on and the gauge stayed at zero, started up the jeep and the gauge didn't move as expected, and the check gauges light came on as expected, so I ordered a new unit Tuesday evening (Napa didn't have it in stock) picked it up Wednesday morning, put it in, and the jeep is good to go. It was a pretty easy swap too.
<img src="/forums/images/graemlins/cheers.gif" alt="" />
Sean

99 XJ Sport 2 Door, 4.0L, 5 speed, all stock. Daily Driver
79 F150 Standard Cab Short Box, 400ci, NP435, NP205, 35" SSRs