See " replace Window Motor" link at upper right of this window for general steps, also described repeatedly in archives of this form for this and other cars.
Some intermediate steps peculiar to GM cars not covered in the link above may include needing a set of Allen wrenches on hand to loosen the tiny set screw holding a manual side mirror adjuster in the door panel. GM panels are attached to door with nylon pop-out fasteners. Removal tool is shown. A screwdriver will work, however.
Also, be prepared to drill out and cold-chisel off rivets to remove the regulator and motor from the door and replace them with nuts and bolts of appropriate size, also to remove motor from regulator if you're not replacing the latter.