my bet, you are going to NEED to be able to pull this battery out. you will need to clean under the battery compartment and to take a good eyeball the cables.
however if you find the truck really is electrically clean, then checking the inputs to the logics is the next step.
I would also say, that it may be from the explanation of the symptoms, that what the problem is, could well be related to the accelerator box and linkage,where the pot is not operating but the start switch and 1a switch is, but checking the inputs will tell us that..