Your at a lack of information.
The truck likely has an anti theft system called PATS.
These systems 'marry' by code to the PCM.
You cannot replace either one with out a reprogram by a dealer.
Also the keys have to be reprogrammed.
The system was design to be nearly fool proof such that you cannot work around it.
As to the fuel level gage, a look a the DTC HEC code may tell what the situation is.
Could be the dash, could be the sender on the fuel pump or harness in between.
Sorry you would like it to be easier but welcome to the computer world.
It won't get better any time soon.
If the dash diagnostics can be accessed, step to the fuel data readout and see what the value is. The number is a decimal readout to an Octal number base.
Readings are 0 to 18 is a short (a fault)..
54 is low fuel, 41 is E mark.
93 is 1/4 tank.
138 is 1/2 tank.
178 is 3/5 tank.
215 is full tank.
255 is an open sender (a fault).
To access the dasd diagnostics, push the reset **** in and hold.
Turn on the ignition swoitch to RUN while holding the reset in for about 5 seconds then step through the sequence using the rest until you get to the fuel readout, and note the value.
If this works, you can see the fuel level anytime without the gage working but not on a continious basis.
I think you can see by now that in this day and age, the systems have to be looked at in this manner or you have no idea what is going on.
Dealers techs have to do it the same way.
The designers gave thses ways to look into the systems so they have to be used.
Good luck.