I recently replace one next to the entrance doorway. With the top all the way up I removed a section of the wood paneling inside directly opposite of the guide and then from the inside I drilled two fair size holes in the outside fiberglass siding in order to unscrew the old guide and then I put the new guide in place from the outside and then from inside I screwed it in place. Filled the holes in the siding (fiberglass) and replaced the small section of panel inside. With top up or down you will never see the patched holes on the outside fiberglass. One camper mechanic was telling me to jack the entire top up off of the bottom and do a lot of other really hard work. My way was quick and very simple and it accomplished the mission. Did not have to jack with cables or pulleys.