2003 Buick Lesabre How do you replace rear window regulator

Hi, my window made a clicking noise when I lowered it. It wouldn't go back up afterwards but I could move it up with my hands with no resistance and taped it up. When I press the button I can hear the motor and can feel something hit the window but it doesn't raise it. Does it sound as if this might be a regulator gone bad? How difficult is it to remove the door skins to get access? My dealer charge $500 when the driver's side went last year so I'd like to do this myself. Thanks in advance,

John