Almost a brand new camper I would have the skin replaced.
Adding a door just increases a place for water or cold/hot air to get into the trailer. The door has little insulation value and is another hole into the interior from now on.
Looks like just the one panel was damaged and is low down which is good. The trailer mfg should have that panel.
I've used this place several times in my mobilehome/rv repair business.
http://www.macsaluminum.com/.
You should be glad it wasn't a gel coat or other non metallic bonded assy. Now its just a simple skin replacement