There is a whole section on the website that deals with a lot of this, its called "
Lighting & Electrical Projects &/or Demons in Your GMC".
Start with the page, "
Some Good Wiring Advise"
As for the headlights, there is a circuit breaker built into the headlight switch, these get old and will trip making your headlights look as if you installed a flasher in the system, you may need to replace the main headlight switch. There is not a fuse on the headlights.
after a new switch you mite want to try the "
Headlight Relay System" to keep the power draw down on the switch.