If I buy a shield from SparkFun XBee Shield - WRL-12847 - SparkFun Electronics, do I need a breakout board as well? I am assuming the shield does the breakout board and easy installation of the Xbee?
do I need a breakout board as well?
No, you don't.
If/when you initially configure your XBee using the computer,
you might also want to get a USB adapter for the Xbee.
one of the choices is sparkfun's "usb explorer", but IMO that one's expensive; I've seen significantly cheaper ones.