The window track on my kia optima 2001 needed replacing when i got the car at 89K. It was only $17.
To the best of my recollection, the door panel is held in place by a series of
1. philips screws that tap into a plastic 'nut-clip'
2. fasteners that 'pop' in
3. and the upper edge that acts like a lip by the window and door.
First, do this when it is warm--plastic is easier to work with when things are freezing outside.
Then pop those little buttons out-- I think two near the rear of the door panel and two towards the front. you need to remove the the plastic cuppy thing that acts like a door handle, probably dirty.
Once you have about 6 screws removed , you should be pretty good to go. then you need to pry the door by pulling from the middle and bottom toward the inside of the car. Don't pull too hard--if the plastic seems fully not budging at a certain point, you haven't removed all the screws. Once the panel pops out, you need to disconnect 2 or 3 wiring harnesses (red light in door, door lock, window contorls.) Then lift up