Hi,
What year car do you have and what unit did you buy out of interest? as this is a future mod I would like to look at doing later in the year as well.
I have been researching online for the different installs etc, and on a roadster this is one of the more detailed vids I have found, but I don't have the back storage box as I guess its an early model 2013. This might be of some use for you thought. https://www.youtube.com/watch?v=eAklx6afwKc