I had the same problem with my 2000 Impala except that it was after I slammed the door in a fit of anger. It was simple to get off and to replace the mechanism ($80 from a used parts dealer online) which is what I had to do. It took about an hour.
First tape the window with duct place in place so if you have to remove the clips that hold the window to it's mechanism the window stays in place.
Depending on which door it is, you need to remove any trim panels such as the the manual door locks or window button with a torx bit.Then carefully using two small flat screw drivers and a helper if possible disconnect the the wiring harness from them being carefull not to break the clips off. Behind them may be a bracket that helps hold the panel to the door body with torx screws also.
You need to buy a GM door panel removal tool. It's about $8 at any auto parts store. It looks like a long very wide flat screw driver that has a forked tip. You slip it between the door panel and body and gently begin prying it away while you feel for the plastic connectors that anchor the door panel to the body. Then get the forked tip around the anchor and pry it off. If some break it's not a big deal you can buy them at the autoparts store also. Just take one to size it up. Here is the link for the tool I have though there are others - http://www.lislecorp.com/tool_detail.cfm?detail=541s
Once the panel is off there will be a plastic shield over the door body. It's held on by tape. Look at it before removing it so you know how it goes back on. Once that is off there are access holes to get at the window mechanism. I had to replace mine. It's really pretty simple once you get started and get the hang of it. Just look at things before removing them and make notes if need be.
Depending on why your windows aren't working, door slammed, electrical, etc depends on what comes next. You may want to check the power at the window switches. See if it is getting power before removing everything.
I hope this helps.