You want to change the main menu? If you wan't to make a custom one, you need either Adobe Flash (or something that can export .swf), some photo tool (like photoshop) and you need to learn ActionScript 2.
Overwrite the existing Main Menu (Menus_Startmenu.gfx or any other name that you want) with your own complete menu. Then edit MainMenu.xml with any changes you need (Game\GameData.pak\Libs\UI\UIActions).
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