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
Cut the roof front header panel in corresponding locations to fit the
remaining original panel. The sectioning joint should be trimmed
to allow a gap of one-and-one-half-times the metal thickness at the
sectioning joint.
Create a 50 mm (2 in) backing plate from the unused portion of ...
Wipers and Washers
Specifications
Wiper/Washer Schematics
Windshield Wiper and Washer Switch Replacement
Preliminary Procedure
Remove the steering column trim covers. Refer to Steering Column Lower Trim
Cover Replacement.
Windshield Wiper and Washer Switch
Procedure
Disconnect any elect ...
Rear Side Door Outside Handle Rod Adjustment
Removal Procedure
Remove the rear door water deflector as needed. Refer to Rear Side Door
Water Deflector Replacement.
Use a flat-head tool to open the clip from the threaded rod connecting
the lock to the outside handle.
Adjust the travel of the handle by removing the threaded rod ...