Just wanted to say my car had a similar spot of what appeared to be adhesive residue on that panel, as did another car I test drove and at least one other I saw on the dealer lot. I tried all sorts of things, to no avail, so took it to the dealer figuring if they screwed something up they'd be liable for repairs. I don't know what they used but they got it off without damaging the panel.

As for painting and prep, Dupli-color makes paints specifically for vinyls and plastics as well as a prep wipe to remove any dressings, etc that may have been applied. I did this on my old Miata but it was still a royal pain in the **** to get proper adhesion and I've seen several other folks struggle with interior painting. Might be worth a trip to a good body shop for a little chat.