i heard there was an update for it , but how do i go about getting this update? because i didn't get an automatic update.

So long as you're signed into Live when you start up the game you will get the update. If you already have it, then maybe you have to beat them again? Not sure... Also, if I were you I'd make sure that you get every other achievement first (particularly Music Mastero for there's a glitch that causes nots to dissappear... Unluess they patched it.)

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The glitch is: If Banjo collects some notes on the Monster Mansion puzzle they disappear in the real level, so make sure you have collected all notes in Monster Mansion before.