Are there user friendly guides and tools available?
No, you came to the wrong neighborhood ;P. Exporting to .rgm/.rga is a pain in the ass; There's only one exporter out there for 3ds max 7/8, so all animation/rigging/setting up maps has to be done in that version This used to be fine, until most of us upgraded to win10. Let's say win10 doesn't like 3ds max 8, there's stability issues, random crashes and display bugs. There were a lot of tutorials on RelicNews, maybe you can find them on webarchive. We also have an internal one, I'll talk to the other devs whenever we can make those public.
Editing gamefiles is easy, no one has access to the sourcecode of the game though. So we use Corsix's Mod Studio to edit units and stats (basically like a giant table editor) http://modstudio.corsix.org/