The old screen can be removed whole, mine was - albeit it will crack etc. Just needs careful cutting, a windscreen fitter will want the screen out in minutes, on these might take an hour of careful cutting.
It will need the dash top wood out to give access and to stop the wood getting damaged, there are no seals on the Aero S1 (certainly not on mine or on any parts diagrams when I spoke to Morgan), the glue is basically the seal so it is a right pita to put in place and then form a seal with tape and tools/fingers while it is still malleable. They used Tiger seal on mine but I believe Wurth Bond & Seal that you suggested before may do a neater and better job as it dries smoother and in a matt black, the working time is the problem though, as soon as it starts going off you can't smooth these glue's out and you get a rough finish.
That or maybe see if the factory can do - I would imagine they are used to installing all the weird and wonderful glass for Morgan's
