Much depends on who is doing the troubleshooting. If the dealership has an electrical specific guy then that may be the best bet. A good independent shop that specializes in electrical repairs is a possibility but if they don’t have a factory wiring schematic this could mean they’re wandering in the desert while looking for the problem.
Just being curious, how about some details as to what problem the truck is having along with the truck mileage, etc.
Many times what is perceived to a be a major problem often turns out to be minor.