Are all the lights out? Start with the basics, are the bulbs/fuses in good shape? Does your truck have an aftermarket radio? Maybe the old feed to the radio is shorting out. Are you getting power out of the light switch? Are the connections good? If so, then start tracking down the wires. Oh, all the wiring for the dash lights should be behind the dash, not in the engine department (although lighting wiring will run to the engine compartment).
Most manuals (and you may even be able to search on-line) have an electrical diagram. This will help. I reccomend you find one if you have to start chasing wires.