some of that is stored in the item file itself. the value model variation in lightsaber uti's tells the game to load this model for this saber.
the itemfile(.uti) also contains references that allow the game to load the description and item name. the things that detremine this seem to be description, descidentified, and localized name. these values do not list the description, they simply point to the strref of what does. so it seems they are there merely as references to other files that are loaded for the description and name. i have been able to change things such as this. like i turned the environmental bastion armor into eaxr kun's armor with the description, icon, and appearance of exar's armor, but with the upgradable status(which did not show up in the description) and abilities of the bastion armor.
however i have read in another post that item descriptions are stored in the dailog.tlk file and they can be edited using the .tlk editor from bioware. i'm planning on checking this out very soon.
here's a link to that thread:
http://www.lucasforums.com/showthread.php?s=&threadid=121918)