2003 GMC Sierra 1500 Pickup Owner's Manual - Page 444

3. Press the release tab, if equipped, and turn the bulb socket counterclockwise to remove it from the taillamp housing. 4. Pull the old bulb straight out from the socket. 5. Press a new bulb into the socket and turn the socket clockwise into the taillamp housing. 6. Reinstall the rear lamp assembly. 7. Close the tailgate. 5-69