Soak the threads (visible from underneath) with PB Blaster, several times for several days prior to pulling the bed.
The bolts are LONG and the threads are likely rusted badly. Use a breaker bar.
You can start the truck and pull the fuel pump fuse (or relay) and let it run till it dies (to relieve the pressure). The schrader valve should be on the fuel injectors' fuel rail.
When you reconnect the lines (reinstall the fuse or relay you pulled earlier, obviously), just turn the key to ON 2 sec, but don't crank, then OFF at least 10X. That'll run the fuel pump about 1 second each time you go key to on and will prime the fuel rail with pressure. Same as if you ran it out of gas.
Welcome to R-F !!!