It can be rather simple, and this is what I have done in the past.
Copy your iTunes folder from inside the Music folder in your Home Directory onto an external harddrive.
After your new Mac is all setup, replace the iTunes folder in the same location with the one that has all of your music and apps from your external HDD.
When opening iTunes, option-click, allowing you to locate your iTunes library.
Done!
Another way is to do a Time Machine backup, and I believe you can restore that backup onto the new computer but that will do ALL times (Pictures, doc's, music, etc..) Don't know if you want to do that.