Another method to remove the screen is to open the sliding window and push
down and inward (towards the inside of the van) on the bottom of the screen
frame as close to where the fastening tabs are on the screen as possible.
The screen should just pop out without having to force anything or having
to use a crewdriver and risk breaking the tabs.

BTW how are you going to refasten the screens to the plastic frame?  I
have to do the same thing and have not decided how to do it yet.  Also I'm
trying to figure out a way to improve my fram so the mosquitos cannot get
by the space between the fram and the sliding glass.  I'm thinking right
now of somehow fastening some of the fuzzy weatherstripping to it to make a
mosquito tight seal.  Anyone have any advice here?

Pascal
'84 Westy