If you are here to find out if Titan: XCIX: Part TWO is still in production ... it is!
Yeah, the textures are COMPLETELY custom, i should know cos i made them ;) Never played System Shock though but if you need further proof go check this out ...
I might be slightly biased but this mod rocks :P Good stuff mate!
The best place you can learn to use hammer is ...
... i do believe there are video tutorails there, but there is also a massive wealth of knowledge in the tutorial section of there forum.
Enjoy and good luck!