I think the modding guide provides a general information and possible to find mod guides on stickied forum topics. They may be slightly outdated for Maya 2020 etc.

If you know how to rig skeletons from this game and do the weight painting to your models and then aling them in the content editor by importing them in collada format. You are pretty much ahead of most mod makers.

The general knowledge of mod makers are circumstantial, if catch the attention of the good all knowing people you may get some help. It's mostly here and at paradox plaza people. A discord channel exists but to my knowledge its live multiplayer who use that for playing.

My own knowledge is okey, but I mostly get my info from the mod guide so it's essentially a repeated info. However I suggest to look for Arnout dark elf race template mod on workshop as it's possible to open and see what changes are made to each required rpk in that mod to make a new race.

Hey, yeah I found the modding guide, it seems quite fleshed out which is really nice to see! Thank you so much for the information, I will see how I go getting a custom asset in-game. I'll be fine with rigging the models to the provided skeletons and such, the only part that may be a bit of a challenge will be the texturing as I've grown accustomed to the modern PBR workflows using the Substance Suite and such, it will be interesting doing traditional texturing again!

Thanks again!

No Discord (and there was never a modding community big enough to sustain a Discord or similar). The most active forum is probably this one for modding: https://forum.paradoxplaza.com/forum/forums/age-of-wonders-iii-modding-and-map-making.1022/ though it's more or less equivalent to the Steam one (but I personally very rarely check the Steam Moddig forum).