More info on playing online with a modded 360?

Whoops...this is kinda the wrong forum (i think so anyways), can delete this if you want.

I read the stickies and learned some things, but still looking for some user-help (you're the user ):

Been looking into getting a 360 Elite console. I always like to mod consoles, but I also like to play online. The elite bundle I'm looking at comes with Madden 08. I'd definitely want to play that online, but could I play it online while using a modded Xbox? Even though Madden 08 would be an official copy (not an illegal backup I mean), would Microsoft still ban my modded 360 from playing online? Is there a way to mod an elite 360 so it doesn't get banned from Xbox Live? Thanks.