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
Remove rear end upper panel extension (1) from service part.
Cut the body side inner 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
jo ...
Power Steering
Specifications
Power Steering System Bleeding
Note:
Use clean, new power steering fluid type only. See the Maintenance
and Lubrication subsection for fluid specifications.
Hoses touching the frame, body or engine may cause system noise.
Verify that the hoses do not touch any ot ...
Horns
Specifications
Horn Replacement
Preliminary Procedure
Remove the front bumper fascia. Refer to Front Bumper Fascia Replacement.
Horn Nut
Caution: Refer to Fastener Caution in the Preface section.
Tighten
17 N·m (13 lb ft)
Horn
Tip
Disconnect electrical connectors.
St ...