Just to check the gauge itself, if you can get to the connector under the truck.
There should be a 4 wire connector:
Pink/black wire is power for the fuel pump
Black wire is the ground for the fuel pump.
Yellow/white is for the sending unit(fuel gauge)
Orange is the ground for the sending unit(fuel gauge)
When you disconnect the connector and then turn the key on, the fuel gauge should go to FULL or to EMPTY, all the way one way or the other.
If you ground the Yellow/white wire, (instrument side not fuel tank side), the fuel gauge should do the opposite of above, either FULL or EMPTY, all the way.
This means the gauge is good and the wiring is to that point.
If gauge gets stuck at 1/4 tank then gauge is most likely the issue, or the yellow/white wire has a partial grounding, which would be odd.
If gauge test seems to work as it should and gauge still only goes to 1/4 and not below when tank gets empty then yes, you will be pulling the tank out.
The in tank gauge system has a float but also an anti-slosh circuit, this prevents the gauge from bouncing around when going around corners or up and down hills, this circuit can fail, also the float and its resistor wheel can fail.
There is also a "bag" in the tank to prevent debris from getting sucked into the pump, good time to change that as well.
Get Ford replacement if possible, less expensive units tend to last only a few months to a few years, and they are a pain to replace even if they give you a year warranty.