A lot will depend on if you can find a body shop that can pull that out from the outside or not. If they need access to the inside of panel, that means whatever is on the inside would need to be removed and reinstalled after the repair. The interior work would have to be at an RV shop, I think, as a body shop won't want to mess with it.
Could get very expensive, and depending on the value of the van, the insurance might total it out. You could buy it back pretty reasonably and still get it fixed, but it would carry a salvage or rebuilt title which would reduce it's value.
It appears there must be a filler panel in there where a sliding door would go and the seam has opening up, so the whole filler may need to be replaced.