its pretty easy, i used the hot swap method, cos im cheap like that!
you can add a usb port to your xbox controllers, seeing as how they just use a slightly modified usb input, then you can just transfer the files via a compatible usb stick, rather than seeking out the action replay kit, which, as far as im aware is the only other method of soft modding.
the thing is, not all usb sticks are compatible, there is a list on the web of which ones are, dont have a link though so youll have to google for it.