my window wont close anymore

i press the switch to wind it up, and half an inch from closing, the thing jams. it bounces up and down like its rebounding off something metal like.

anyone ever have this problem? i'm afraid i'm going to have to take my door panel off (HOW DO YOU DO THIS?) and take a look see because for the first time in forever, it rained in socal and my seats got soaked h: