I currently have a '09 GT, never figured out how to use the Navigation System (too frustrating) and the Bluetooth connection to the phone has broken. It doesn't allow the phone to be paired with it. I would sugguest to install an after market head unit as noted in the audio section for about the same price and many more features... Bluetooth- phone, music from phone, google maps (which think is the most accurate), it may mirror the screen and play movies, plus a backup camera feature.
I just use mine as a player for pandora via the aux connector.
What I've done to my '09 GT:
Dyno- matted and sound insulated entire interior (took one month/everyday/retired)
New JL Audio TR 570-CXi Speakers
Stock Navigation head unit= sounds great, no need to put in amplifier, some wind and road noise still...but much,much
quieter!!!