Nuevo ES Damp Problem

Looks like I have a problem with damp on my Auto-Sleeper Nuevo ES where wall joins floor behind drivers seat. 

Suspect side panel seal between cab and living area. If seal needs replacing or resealing is this a diy project or will it need a professional?

Had same problem with our Nuevo shortly after buying it, so luckily was under warranty so dealer had the long seam resealed all the way round. No problem since.

If you can remove and replace seal around a bath or shower you should be able to do this but you will a warm dry couple of days or barn to do it in.
The sealing may not however be the problem if your van has been letting in water for some time there might be timber decay at the back of it
David