To import the on-disc songs from Rock Band 2 into Rock Band 3, you need to go to the "Get More Songs" menu in Rock Band 3 and select the "Redeem Code" option. The code you need is printed on the back of your Rock Band 2 instruction manual, and the download will also cost 800MSP ($10). This 1.9GB download will bring all of the RB2 songs into RB3 with the exception of -
- AC/DC - "Let There Be Rock"
- Journey - "Any Way You Want It"
- Metallica - "Battery"
- Red Hot Chili Peppers - "Give It Away"
- Soundgarden - "Spoonman"
All other DLC, including disc exports from Rock Band 1, LEGO Rock Band, and Green Day: Rock Band will already function properly in Rock Band 3 as long as they are already on your hard drive (as in, you've already been using them for Rock Band 2). If you don't already have them, the import process for those games is the same as above, but you'll need the codes from each game's manual, obviously.
Also, if you no longer have your Rock Band 2 instruction manual, or your code has already been used, you can get a new code from the EA Rock Band support site (Feature currently not active but coming soon) or by calling an EA hotline at (650) 628-1001. These two options were revealed through the official Rock Band Twitter account, so if they don't work blame them, not me.