GM parts Direct, are OEM parts, and are more expensive...
The four at RockAuto, are aftermarket.....when I see something sell for 42 bucks, with all those switches, makes you wonder(Chinese made?)......
Replacement is easy....grab the top cover near the Steering Wheel and lift up....rear part just slides out of hooks.....make sure key is out of ignition.....one 7mm screw on top.....pull unit upward......disconnect the harnesses......when installing, you must depress the contact on the back when installing....there are tabs that help with alignment during installation....