My wife's 2001 Right Front window stopped working about half way down. You state it no longer works, but you don't mention if it "was working" and stopped part way down. Can you hear the motor trying to work? If so, you likely have a bad window regulator..The Plastic drive gears usually snap & you have to replace the whole regulator.This is a weak spot in the Lesabre's from 2000 & up a couple years. Do not get a used one, as they will eventually break too. You can buy an brand new after market regulator assembly ( with motor) for as little as $90.00. I've replaced both right front and right rear already..I did it myself & saved big $$ on body shop labor. I bought my from this salvage co. 320-363-7504
Most likely the window accuator is bad.
They operate on a spooled cable system. The cable stretchs and gets loose then it bunches up and gets a backplash effect like on a fishing reel. It can't be fixed. all you can do is replace it and hope the next one will last longer. A very poor design! I also bought aftermarket ones from a used auto parts place. They were from Tiawan. They worked for a short while and then did the same thing. A very common issue. I feel GM should stand behind this design error since it's "SO" common.