I've done it to my sleds. Loosen the track off to line up the slider with the window. Remove the front slider screw. See if you can move the slider rearward, if not you may need to pry something at the front to loosen it then smack it with piece of wood etc. Get the slider into the window, use generous amount of wd-40 on end of slider and track. i like to just get the slider into the window then i go to the front and use the mallet and wood to pound it out. Once it gets going it comes out easy. Reverse to put in new one. Keith.