YouTube and CakeTV have a BUNCH of free videos on lots and lots of different aspects of doing things in Sonar, and there is also a ton of helpful content that has been posted on the Sonar forums that will cut down on your learning curve somewhat.
Once you install X3a, download and install the latest maintenance updates, which are in release X3e. There is no need to install X3b, c, or d, just X3e after you complete the initial install of X3a.
LOTS of new functions, the Pro Channel, Melodyne, and comping, and lots of other things to keep you up late at night.
Have a BLAST! :)
Bob Bone