Many questions are repeating themselves here on the mod boards, and everywhere else on the forums.

Search the modding board. Dont be lazy. It is not that hard to do. Chances are the question you want to ask has already been asked and answered.

There are some tutorials on the modding board right now that fell into the back pages over time. Heres mine on how the Sins textures work Texture Info

You can ether use the Forge Tool suite due to be released soon to import models, or use Code Herders model importer. There are issues with code herders tool, and he is working to fix them, but the tool works. Link to Code Herders Tool thread

If you use the Forge Tools to import models you will need ether Softimage XSI, or its freeware version called MOD TOOL. This is because the Forge Tools only support the dotXSI format of Softimage. The reason being is that there is a certain way Softimage handles shaders for the game that other modeling programs do not support.

More info will be added as it is found.