There are a few ways.
With the Xbox 360, you can buy them.
With anything, you can hack into your platform and add them in. I don't recommend this because it can ruin your game and system.
Not.
It depends if the Guitar Hero 3 songs were released as DLC on GH: World Tour. There is no way to directly import songs from Guitar Hero 3 onto World Tour.
NO
no
You can find a full list of Guitar Hero 3 songs from the Related Links below.
unfortunately, no, it only works on either Mac or PC
no.. not at this time
Officially, you can't.
you cant
I am not sure but I know you can create songs on guitar hero world tour. I was searching for the same question. I also know that you can download songs already made at the playstation store. (playstation store/addons/disc based games/guitar hero 3)
First you need to eat a heaping plate of fecal matter.
I think 'Na Na Na' was in a Guitar Hero game.