i don't know how much experience you have with modding, so i'm just going to lay this out in baby-steps, as if i was explaining it to an absolute beginner. don't be offended if some steps seem really obvious.
Once you've downloaded and installed that, open it up. The filepath you'll want to follow should look something like this: "C:\Program Files\LucasArts\Star Wars Jedi Knight Jedi Academy\GameData\base\assets0.pk3"
Open up the assets0.pk3 file with Pakscape, and look for the folder called "strings". In that folder, click the folder labeled "English".
In that folder there is a word document called "MENUS". copy this, and paste the copy on your desktop.
Open up this document. Click Edit>Find on the toolbar, and type in "BLASTER_PISTOL".
highlight the "blaster pistol" line after "lang_english" and hit backspace. name it what you like. DO NOT change the top "blaster_pistol" after "reference". leave that how it is. only change what is in the quotes. make it DL-44 or whatever you wanted.
now, save the file, and exit.
cut the file from your desktop and paste it back into Pakscape, replacing the old "MENUS" file. Save the folder in Pakscape and exit.