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 WarningAir/Wind Noise
Special Tools
CH-39570 Chassis Ear
GE-41416 Ultrasonic Leak Detector
Warning: Refer to Assistant Driving Warning in the Preface section.
To analyze a reported windnoise condition, test drive the vehicle to
determine the origin of the noise.
Choose a regular route with smooth and strai ...
Power Steering Gear Inlet Pipe/Hose Replacement
Removal Procedure
Remove front bumper fascia. Refer to Front Bumper Fascia Replacement
Remove as much power steering fluid from the remote power steering fluid
reservoir as possible.
Place drain pans under the vehicle as needed.
Remove power steering gear inlet hose bolt (1).
...
Installation 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 ...