Here's a post that shows how to remove the outside trim on either side of the windshield.
2008 Sightseer A-pillar trim removal with diagramI'd bet that yours is identical. There was a screw under that holding the end of the windshield top rubber trim.
I just went into our 2008 Sightseer and noticed that I can see the bottom side of the sealant that holds the windshield in if I use a strong flashlight and put my head right against the windshield. It may be worth your time to take a look before you do much more. Best of luck.
Al
