They are stitched in at the front and ride in the channels at top and bottom. All you have to do is undo the stitches and slide it out.
Going back in any industrial sewing machine can do it. It has to be able to sew right through the plastic window...so a bit much for the wife's machine. I took mine to a local upholstery shop, who charged $20.
By the way, the design will always scratch. The rubber seal rubs against the soft plastic, so to keep them looking new plan on never sliding them open!