While I got practically all the data recovered from an old project, I'd apparently need to use the new 9-verb template instead of the old Proskritos SCUMM GUI. Is there a way to apply the new GUI template to an existing project, or to export all the sprites, views, dialogs and so on to a new project?
You can get an old game to open in AGS 3.2.1 by opening and saving it in 2.72 first. You can get that here (http://agsarchives.com/engine.html).
As far as applying the new template to an existing game; if you extract the template's scripts, sprites and GUIs, it should be possible. Very likely less work than rebuilding the game.
On the other hand, you'll have a really messy game on your hands, full of old code, obsolete stuff, etc.
You can easily export the sprites and backgrounds from your old game and rebuild it. It's what I would do.
Dialog scripts can be copied in the editor.