This is a separate thread regarding a program I just found out about. It's called ResViewer for Flight Unlimited 3 by Gideon Pertzov, and it can export and import files that are packed inside LGS' .res files. Even though it's primarily made for FU3, it will happily open .res files from every game that uses them (System Shock, Terra Nova, Flight Unlimited 1-3, Thief 1,G,2).
I haven't tried editing any assets and importing them back to see if it works ingame yet, but replacing sounds and textures in System Shock or Terra Nova should be easy.
The source code for the program is also available, so someone could make a version that correctly identifies the filetypes of non-FU3 games.
Cool, I just found this, thanks for sharing. The link is alive stil, so now I am off playing with ResViewer
Regards
/Aero