Head Unit
Mate search the forum, there is a thread that shows you how to remove the dash.Its quite easy when you see the photos.
Make sure when you purchase a new head unit that you get all the interface leads for it.
I have just bought a Sony XAV601Bt unit and got all the leads made by AERPRO.The aerial input is not like a standard aerial connection as Nissan have changed to an ISO unit.
Hope this helps.