I don't know if this post will be any help to you, Roidon, but we also planned to not only replace the old vent with a new one, but add another 2way vent fan. We have a 13' scamp
that has the original vent that is yellowing and starting to crack. I would be happy to see any advice in this area as we are not sure what we are getting into at this stage either. I do plan to install the awning
rail and some inside upper cabinets first, to get the hang of working with the fiberglass and other materials before we take on the bigger job of replacing/installing the vents. I know it will be a lot of work, and important to get the seals right esp. with cutting a new hole in the roof.