Make sure any screws are off first (usually in the armrest area). Usually breaking the clips is not the issue, its breaking the housing on the panel the clips are snapped into. All of the clips install in a cross car direction ... in other words, disengaging them is done by pulling straight out from the door. On my 2001 Bonneville there are 2 clips in the armrest area. Once all the periphery clips were disengaged you have to lift up on the door panel to disengage if from those 2 clips.
Make sure you buy butyl tape to reseal the plastic watershield, or you will have water leaks ( Butyl Auto Glass Tape 1 8 x 1 4 Street Rod Hot Rod Rat Rod Custom | eBay
). When you install the new butyl tape make sure you follow the exact same path the old tape followed.
If you haven't purchased the new regulators yet, take a look at www/rockauto.com. If you do purchase from rockauto, search the forum for "rockauto discount code". It'* good for 5%.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)