(1) Are there any manuals or tutorials on getting started with modding?
(2) Can I base my mod on FAF? That is, FAF would be the start of a new mod and I would change that by hooking (destructive and non-destructive).
As a first step, for learning, I would change parameters of units and build-permissions (what can be built in each factory at each level). Initially, I would not necessarily be trying to build a good, playable mod at first try, but just making changes for the purposes of learning to mod FAF.
What kind of mod to make? In my opinion, a good mod needs a theory and a theme. Of course, it needs good theory and theme. By "theory and theme" I mean something that gives the mod a consistent set of design ideas, good balance and sets it apart from FAF and the other official mods. Nomads is an example. The theme by the maker(s) was to add a new faction. The theory was that the new faction needed new build, unit, weapon and performance characteristics which would set it apart from FAF and other mods and which would still be balanced.
I have some theories but it's too early to mention them in detail. But I will ask some questions. Would people like to see these in a mod?
(a) Start with a considerably nerfed ACU? (Ideas: Less HP and slower walking but have upgrades to improve these capabilities).
(b) LABs stay useful longer in opening.
(c) Only land and sea factories can make engies, not air factories.
(d) Air and navy, factories and units, more expensive.
(e) Ground AA weaker to account for item (d).
(f) Bots faster over broken ground and able to climb steeper hills than wheeled and tracked vehicles. (Salems won't get these buffs.)
(g) T2 Hover units lighter (less HP).
(h) Wheeled and tracked vehicles faster over flat and open terrain.
(i) Nerf veterancy upgrades for ACU and Experimentals.
(j) Less percentage from wreck reclaims.
Just a few ideas. Don't know if I could code them (when I learn).