Power Window Gears

I have a 1994 Convertible, and the back passenger side power window gets stuck in the down position. When I checked it out, I found that the gear that the motors gear turns to move the window up and down, had about 4 teeth worn down. The window works fine as long as you don't lower the window all the way so that the bad teeth get involved - they are at the very end of the gear. Does anyone know where I can get a replacement for that gear, and how involved it is to switch it out?

Thanks,
Larry