OK. If you want good tuts on this, go towww.xbox-scene.com, hit tutorials on the menu, and you're set (look for softmod / no-modchip modding). Basically, you need Mech Assault, 007: Agent Under Fire, or Splinter Cell (original version, not platinum Hits, since the PH version has some security holes fixed up.) You buy a gamesave thingy called Action Replay, and an official memory card. You get a gamesave exploit (it's explained in the tutorials) and load it onto the memcard with Action Replay, run the exploit through the game, install the modded operating system, and woot woot! NOTE: Unless you do a rollback, you can't go on XB Live without gettin banned, and I'm pretty sure you may get banned even with the rollback. However, it IS better and cheaper in the long run to get a modchip; you can get someone to do the soldering and all that for you if you want, or you can get a no-solder chip (my recommendation is the Xenium ICE). Do a lot of reading before you start, BTW. Lanche out.
Yeah, just read the tuts ^_^. BTW, the FTP that you access (info inside the Xbox-Scene tut) has almost literally everything you'll ever need for softmodding. It's pretty cool... all modded operating systems are Linux-based, as well as the Xbox OS. You can load linux apps onto there and run them... you can have doom (the original), pong, etc. Fun stuff.
If you found about this now.. Sad. It's Illegal in the states, I'm sure.. But people do it. Theres a really pop company that does it, very well too. Most chips you need to solder, the non-solder ones kinda suck. I'd say you get someone to solder it for you, because you sound like one who would f*ck up