Changing out the motor is not hard--but the motor is not likely the problem. The switches carry current and have rather soft contacts which burn/build up a layer of carbon(?). Check the operation of the window switches at the rear doors. If they work consistently remove the screws holding your choice of armrest and slide the switch out towards the door (kinder to the plastic than trying to just pry the switch out). Do the same with with the driver's door switch panel.
The switches just pry off the trim panel. Plug the rear switch into the front window harness and give the motor a test with the new switch. Snap the new switch into the panel and you're good to go.
You can then "overhaul" the reluctant switch. They just pry apart and have pins and slots to assure alignment on reassembly. Inside you'll find stamped metal "rocker" contacts, and a spring and ball for each. I scrape the crude off all the contacts and use either grease or vaseline to hold the parts in place as you snap the works back together. -- Dave