2001 GMC C1500 No headlights

Welcome to the forum, as far as the headlights, check for voltage and ground at the headlamps. The orange wire is voltage, goes hot when you turn on the headlamp switch. The ground circuit, yellow wire is ground for low beams. Puple wire is ground for high beams. I'd check for voltage first. There is a headlamp relay in the underhood junction block. Voltage for load side of relay, is hot all the time. The voltage for coil side of relay comes from the headlamp switch. You need to be sure the battery has a full charge and the connections are good.