how do u do that and will this work if the other box doesnt have it

I did this once, i could also change the names of the vehicles (ie, warthog = puma) etc and the weapon names (sniper rifle = jiggy, just a joke my friends and i have).

I just got bored and opened a hex editor on the map file. I looked through, or searched, can't remember but just changed stuff as i went, just remember to leave those spaces there and fill then im empty spots.

Edit: It will only work on ur box and probably have network issues on other boxes cos the map is different, unless u try copying it over to the others, but i havn't tried it.

text, texture, and sound changes shouldnt give a sync error.

Yeah, it shouldn't. The game has the whole alphabet programmed into it so changing text doesn't make a difference. Change scenery for something like glasswalls could potentially get out of sync. Although LOTS of glasswalls have been using the in game projectiles like the Needlers.

google "halo xbe hacker"
its a program that allows you to change the text strings in the halo default.xbe
i used it myself to change game text and it doesnt error the other box