I just pulled an AVIC-D3 out of my Sonata before trading it in for the Legacy.
It was a great HU however for the past year or so the bluetooth functionality started failing and throwing errors that could only be fixed by restarting the car (to reboot the HU and the BTB module)
Maps on DVD also was a terrible idea; my kid got ahold of my East coast disc in the center console and scratched it up and Pioneer wanted $300 for a complete new set.
I'm sure they've improved upon this over the past 9 years (thats how old the D3 is)
That all being said, I love the integration of the OEM unit but REALLY wish it had the nav.
Google maps works OK on my phone, but, having everything together would be great.
Would be interested to know if you need to add a GPS antenna to go from stereo to nav... Dropping the head liner surely isn't going to be fun.