Re: failure to d'load update
There is no code for the update, it's free for everyone who owns the game.
The only codes that come with the boxed version of Xbox 360 is a code for two in-game item packs and a free trial of Xbox Live Gold.
Are you sure that you have an Xbox Live Gold subscription? (You do not need the Xbox Live Gold trial code if this is true)
An Xbox Live Gold account is required to play.
Perhaps you should try downloading the Legends of the Lawn DLC from the Xbox Live Store instead.