Have you been syncing with another computer before this? If so, copy the entire iTunes folder from your old computer to your new one using one of the methods outlined here: http://support.apple.com/kb/HT4527. This will transfer your iTunes music and allow you to sync with your new Mac without losing any data.
To have EVERYTHING as it is Now...
From your OLD computer...
Copy your ENTIRE iTunes FOLDER to an External Drive... and then from the External Drive to your New Computer..
Full Details Here > http://support.apple.com/kb/HT1751
An Added Bonus is that you will have a Backup of iTunes.