But this does require knowledge of the engine which you won't get unless you know C. Putting objects in willy nilly with no thought as to how the engine uses them or might interact with them is ludicrous. You gotta know how it textures, what textures it might use, size of textures, bump map or no bump maps, light maps, radiosity maps, etc. And that's just for the textures. If you want to do modeling you need to know the upper limit of the triangles allowed and then divide that by the number of objects you want on screen, etc., etc. You must know how it culls or why it culls and when it culls. You must know something about the physics engine because your characters and objects will most likely be integrated into the physics engine. You need to know something about scripting as well as 3D mathematics and/or 3D concepts in order to accurately rotate, translate, and move your object and/or set a path for it.
Not true. He never said what type of modding he would like to do. For instance, modding maps in something like Halo, involves no C++, but "Halo Map Offsets" (googleable ), and a hex editor.