Problems with rolling down window...

If you have the door panel off already it`s only 3 bolts to remove the regulator. I`d go ahead and remove the regulator and try it without anything hooked to it to see how smooth it is. This will help tell you whether the problem is in the regulator or elsewhere. While the regulator is out you can manually push the window up and down and see if you can make it bind. The front and rear glass channels should be lubed and checked for proper glass fit. While things are apart a good cleaning and lubrication will help things glide along when you reassemble.