Well, you can FTP the maps to the xbox, but they won't appear in the game. and they won't get rid of your maps, aslong as you make backups when the mod requires a patch to be applied. It's a long and grueling process to add them, because you get to manually add them to the "maninmenu.map" and you also have to "resign" the map you're adding and the "mainmenu.map". Just look around on the forum, you'll find it very fast, it only took me like half an hour to find it.
EDIT: here's the link to the thread
http://files.halomods.com/viewtopic.php?t=31955
The thing that i learned, is that all u need to do is the last parts with DotHalo, and signing the maps, the HexEditor is really not needed, cause Halo picks up the map name, as the scenario name, so u just need to change the name of the map to fit the scenario name, then resign both the mainmenu.map and the maps that your adding, and they should appear in the map selection list. But they won't run, unless u disable the autoupdate.
To disable the auto update go to this location on ur xbox: "E:\TDATA\4d530064\Su" and there should be a file titled "default.xbe", u can either do it the hard way with a HexEditor, or you can just rename it to something else (i just made mine "defaultish.xbe" and it works perfectly).
Just post back if you need any more help
