fuel guage is on full all the time

Pegged past the usual "Full" mark is an indication that there is an open in the circuit. Generally speaking, if the gauge wire is shorted to ground, it will show past empty when the key is turned on. The most frequent failure is the sending unit itself. The very best way to access it is to remove the bed. It only takes 4 people and doesn't require handling any fuel. Do you need the steps to replace the sending unit?

Here is a video on the replacement of the fuel sending unit: https://www.youtube.com/watch?v=N3oC5WJeSX0

From my understanding it had been like this for a while.There are only 35000 on the truck, and I fill it and run it out over the course of about a weeks time. I live in Pennsylvania