Glow plug relay and break pads

Yes, you can just replace the pads. However you need to look at the condition of the rotors. If you have grooves, heat spots, cracks, glazing, or just to thin to use. Then you need to have them turned, to true them up and remove the grooves or glazing, or replaced depending on the condition. bleeder screw is there to remove air from the system. remember to pump your brake pedel several times before you move the truck to extend the calipers and be sure you have stopping power after the pad replacement. Glow plug relay should be under a cover mounted on top of the engine block.