I recently started playing around with the raspberry pi 2.
I followed the guide on lifehacker to get this set up.
The setup is really easy to get going but I did find a couple of commands very helpful.
rpi-update will update the raspberry pi firmware
Retropi is based on Debian so apt-get is your tool for general updating.
Getting a console
when you are in the games menu hitting f4 on a connected keyboard will open up the console.