Answered my own question w/impatience and a little brute force.
For others' reference later:
I found this post on Vanagon window screens:
http://www.thesamba.com/vw/forum/viewtopic.php?t=412537 It appears they are very similar to the Eurovan ones.
I pried the lower-back corner loose, and slid the screen back and forth a bit to loosen it up. Then, pulled hard on the top, and it popped out. From there, pushing down a bit gets the tabs on the bottom clear of the metal frame they are grabbing.
I had to be quite forceful on the top, but be careful on the bottom -- that's where the tabs are that you don't want to break.
Hopefully helpful info to someone looking here at some point in the future.