Hey thanks for the responses!

Like I said, I'm new to this forum but not new to forums in general and I noticed that on these gaming forums (not this one but other 360 sites) people are real jerks. I mean, I'm trying to get some info but you can't find anything because the only answers are... "this has already been answered, do a search". Well to be perfectly honest I don't feel the need to be registered at 50 different site (so I can use search) just to get a few answers once in a while ya know. And even if I turned into a search junkie I'm not a computer nut and don't know the terminology or have the vocab. to efficiently search and find the answers I'm looking for.
So.......Thanks, I appreciate it!
Here's my situation. I've had my 360 for about a year and love it. I think the FPS's are awesome. And I really believe COD3 is probably the best on any platform ever, IMO. This coming from a guy who played Battlefield Nam and Modern Combat before it was popular on blazing fast liquid cooled gaming (PC)boxes with 7.1 1000w for full effect ya know. I really thought PC was the way to go but I really enjoy sitting on the couch in front of the 52" and the sorround blasting much more than I like sitting in a computer desk. So, 360 ftw!
I recently inherited another brand new 360 premium from a buddy who owed me $100. I'm not expecting him to stop by with the money and he doesn't have a place to play it anyways so it's mine to do what I want with now. I know people have modded their boxes but I really don't know much about it. I guess my questions are this:
-What are the benefits from hacking the firmware? Does it run faster? Improve game play?
-How much of a pain is modding the guts?
-Are there any mods you can do which will still allow it to sign on to XBL (even though this one never has yet)
So yeah, I'm pretty much lost as to what to do with this as I am not sure what some of the possible options are. Any helpful responses much appreciated. Thanks.