Welcome on the forum. I would start by talking to people doing such repair work. It might mean cutting a piece of the skin out and glueing on a aluminium plate after the repairs to the wood rot. This is how the wood rot above my door was fixed.
Dean, I don't want to be the harbinger of bad news, but this might not be the only wood rot on your van. I would suggest you firstly look at areas where you can see exposed wood like underneath the caravan. Also push against the walls all around to see if there are any areas where the walls give, indicating wood rot. Perhaps you are lucky and this is the only area, but it is a good idea to try and make sure. I have seen caravans stripped down to the bare bones at our local Camp World so I know it can be done, but I would guess it might be a bit expensive. Good luck and keep us updated please- we learn from each other.
Dean based on what Fred indicated I would take it to a dealer and let them check with their meter to see if there is other wood rot and then give you a quote for fixing the various areas. That way one can save a lot of labour than to do only the portion known about now and may be other areas are also affected. This quote is only to know what the extend of the problem might be.
The areas around the pop up roof could also be an area to check where the brackets screw into the movable portion. Check the area under the step below the door. The 4 corners on the caravan.
I only knew about the most wood rot around my one vent but some ant in other areas. It turm out I had rot on both corners next to the back window. I got two thirds of the roof repaired with new panels on the inside and the structure wood replaced.
Sorry you hit this problem being new to caravaning.
Dean, I doubt very much whether heat will do the trick. If glue that melts when heated was used, it might soften when exposed to direct heat from the sun and the outer skin might come loose. I would guess it is probably a contact type of glue or perhaps an epoxy type. Could you perhaps get a thin sharp knife in between the outside (and inside?) skin and the wooden spars to cut or saw through the bonding? It might be possible to only loosen a small part in order to remove and replace the rotten part. Just be very careful not to crease the aluminium outer skin as you will not be able to get the crease out again. It should also be possible I think, to attach the new spar by glueing it to the existing wood and skins. It will certainly be interesting and probably helpful to people expieriencing the problems if you can post some photos as you go along.