HaloMods "Classic" Read-only Archive

Ok well i have been trying to use hex editor for quite some time now and eveytime i use it and save it, it has an error. And then it screws up my map file and i have to start over. I understand that when using hex u cant use more letters than the original words. So any tutorials available for me to learn hex, or any on just to change the names of guns and crap.

Thank you in advance