Two different plugs go into the top of the pump. One is as you describe. Could be the other one is for the evap system.
Interesting you bring up the sending unit. When the ignition switch is turned to ON, the fuel gauge oscillates rapidly. Reading is accurate, but it just vibrates at that reading, neighbor says it had been doing that awhile before the truck died.
Which color is the pump, which the gauge? I noted that the gauge did not change reading when I unplugged the plugs at the fuel pump.
Our worry is that, even with a new pump, it will still have the underlying condition. Pump starts at inital pressurization, shuts off, will not restart for RUN sequence.