Window Work

hoping for some help,
the windows on my 380 always seemed a little slow, and now the passenger side is really acting up. sometimes goes up and down fine, sometimes goes partially up or partially down. so far it eventualy does what i want it to do, but i know it will at one time become completely inoperable. any poiters where to begin??? how hard is it to remove the door panel,i'd like to start with checking the lubrication i guess.
thanks for any advice and help.