Anyone have any experience with a power window that sometimes goes all the way down when you press the auto-express function on the switch, but other times goes down to the point that 1" of the glass is above the lower level of the window opening? The window will completely go down if you press the power window switch a second time.

I'm sure someone knows for sure but that sounds like a problem with the switch to me unfortunately I know of nowhere besides the dealer to get that part. From experience the door panels come off fairly easy on that car, I did speakers on my grams 07 Lucerne. The window switches just clip to the surrounding trim which clips to the door panel. Just be sure not to break the clips, I did on my old lesabre and they would always flap up and down when the door shut.
Hope this helps some

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Will
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Some of the older GM cars had an express down module inside the door. I don't know if Lucerne is one of them. The car is still under the bumper to bumper warranty, so I may just let the dealer mess with it.