1. I've been intending to do a detailed write-up on how gr2 stuff works, but I haven't had the time to do it yet. For static meshes the workflow is quite simple, you just export a .DAE from 3ds, convert it into .GR2 and create a new resource in the editor. Skinning/animations are more complex and i'd recommend reading the referenced threads as they contain most of the info.
4. There is no built-in tool for this, but you could convert the map into a texture and apply it on a semi-transparent plane as a workaround.
