I looked in the manual and I didnt seem to find anything that could permit me to open a folder on the user's system.
In melScript, there is a command "system ("explorer "...blah) where from within maya you can open folders with explorer by scripting.
Would there be a way to do this with AGS? It would be so that when a screenshot is saved, the savegame folder gets opened.
There's no way within AGS to perform operations directly on the Windows shell (like opening a folder). You could probably do something via a plugin by just registering a new AGS function and then using C++ or C# to actually open the folder.
Major newbie question but is there a current "how to" section for creating plugins? I guess I need visual studio or something? Ive got my c++ for dummies book, maybe I can get myself a visual studio book too...cause its fun.
The official plugin API is written in C++, for which you should be able to just use any C++ compiler. There's no "official" guides of any kind except the Plugin API Documentation (http://www.adventuregamestudio.co.uk/acplugin.htm), and the plugin source itself is a very small non-practical sample.
The API has also been ported to C# if you find that easier to work with, but bear in mind that would require any users to have the appropriate .NET Framework version installed (probably not an issue for Windows-users, but just something to keep in mind).