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:

California Proposition 65 WarningFront Side Door Lock Cylinder Coding (Non Free Wheeling)
The door lock cylinder uses 8 of the 8 cut positions. The tumbler positions are
staggered from side to side, 4 on one side and 4 on the other, are not self-retaining,
and are not snap in.
Note: All lock cylinders for side milled keys have right and left
tumblers. The locat ...
Body Hinge Pillar Lower Reinforcement Replacement
Removal Procedure
Warning: Refer to Approved Equipment for Collision Repair
Warning.
Disable the SIR system. Refer to SIR Disabling and Enabling.
Disconnect the negative battery cable. Refer to Battery Negative Cable
Disconnection and Connection.
Remove all ...
Transmission Fluid Pump Disassemble (6T40/45/50)
Table 1:
Fluid Filter Assembly and Torque Converter Fluid
Seal Disassemble
Table 2:
Fluid Pump Disassemble
Fluid Filter Assembly and Torque
Converter Fluid Seal Disassemble
Fluid Filter Assembly and Torque Converter Fluid Seal Disassemble
...