The screws sandwich the frame pieces together, and the factory normally uses butyl tape to seal the outside frame to the RV siding. Once you remove the screws you'll have to gently pry around the outer frame to loose it from the tape. You can then remove the tape/sealant residue.
You can get butyl tape at most RV stores, but you could also use polyurethane caulking to seal the frame to the RV, but be aware that if you use that, you'll have a real problem getting it off ever again.
Salem 29RKSS Pushing a 2500 Mega-Cab CTD!
Gotta go campin!