For question number one: See the Game Hacking forums for ideas/help.
For question number two: See the No-Modchip Hacks (Exploits) forum.
A decent amount of reading of the pinned topics and guides in those forums will give you a good start. Also note the pinned Softmod topic at the top of this forum.
(And, no, the Xbox HDD file system is not compatible with a Windows PC as it were, so you won't be editing HDD files by hooking it up to your PC).
Please read the Newbie Welcome Guide in this forum, in full, before proceeding.