@bitterman
I think you got a wrong engine to mess with. If you never modded Quake 1/2/3 and have hard time using what's available for Doom 3 (iddevnet, modwiki, TheDarkMod wiki, 3dbuzz and Doom 3 assets itself), you are better off using CryEngine or UE4 (those are the only FPS engine with bunch of docs and tutorials, including step-by-step guides; UE4 is a better choice as it was very active and large community, including pretty good Russia-spoken youtube videos).