More details about the Live Tuning Pack can be found right here.
Quote:
"For gameplay you should notice that larger players cannot jump as high to swat down passes making things look and feel more authentic. In Dynasty mode, it means two things. First, the majority of the teams in Dynasty will be slightly better than before due to having access to higher rated Prospects and slightly better progression. Second, CPU teams will do a much better job of accurately filling their rosters."
I'm pretty sure they're two separate downloads. You need to have Online Pass enabled to get the tuner, but not for the patch. If you bought the game used or are renting, it costs $10 for an Online Pass code. If you bought new, the code should be on the manual.
The patch will download as soon as the disc trys to boot up. The standard Xbox screen will pop up and you select Yes to update now.
The tuner comes later. Once you get to the screen where it says to press start and all the data starts loading a box will pop up and say your tuner set is out of date blah blah blah. Then you select yes to update.
This will overwrite tuner set 1 and you will be up to date.