Navigation Systems

I have an 05 Mazda6, and I want to install a navigation system and/or dvd player in it. There is a place on the dash for a system, but I have no idea where to start. Should I buy a GPS and have it installed, or go to a shop and have them do everything, or is it easier to do myself? Any suggestions will help. Thanks.

I saw a customer come in with a aftermarket nav installed it the head unit was Icons and it was custom because the way they positioned it it opened the center compartment and closed it as well .