Gallo, what I do is take my files out of the Guns File after Reztracting it, and place a copy of them in a TEST folder, there I do the renaming, and inject them back into the REZ which is automatically called .reznew ... therefore you rename your prior .rez to .rezbackup and modify .reznew to .rez
Your way may take a bit less time moving around the hex coding because you are not renaming... but it could be a lot more complicated to new guys. I am familiar with hex coding because I've used CheatEngine & Hlapex on the past.
At this point im attempting to interfere with the client-server communication using hex interceptors from other games (hlapex) ... i've never seen anyone mention cheatengine or hlapex on this game... probly worth exploring.