For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningInstallation Procedure
Clean and prepare the attaching surfaces for welding.
Position the roof rear header panel (1) on the vehicle.
Verify the fit of the panel.
Clamp the roof rear header panel into position.
Spot weld accordingly as noted from the original panel.
Apply the sealer ...
Installation Procedure
Drill 8 mm (5/16 in) for plug welding along the edges of the front
wheelhouse front panel as noted from the original panel.
Drill 8 mm (5/16 in) for plug welding where front wheelhouse front panel
and front wheelhouse overlap.
Clean and prepare the attaching surfaces f ...
Roadside Assistance Program
For U.S.-purchased vehicles, call 1-800-243-8872; (Text Telephone (TTY): 1-888-889-2438).
For Canadian-purchased vehicles, call 1-800-268-6800.
Service is available 24 hours a day, 365 days a year.
Calling for Assistance
When calling Roadside Assistance, have the following information ready:
• ...