Just wondering-Let's say i get Nightfall from a real store.Do i insert my key only or do i boot up the CD?

And now,assuming i buy the key from the Guild Wars Shop.Do i download the entire content OR do i just get the key activated?


P.S:Incase you got confused,i already HAVE the Prophecies version of Guild Wars.I took a break for a year and now i'm addicted again.