Hi all,
I spoke with the person who does audio/ navi installs for my Ford dealer and he said, after some research, that it is possible to install the 2009 factory navi system after the fact without losing any functionality. He did say that there would need to be a lot of rewiring and that the steering wheel controls would need to be replaced. A new antenna would need to be installed as well.
All in all it sounded like a major hassle, and it would cost $3250. Ouch.
I decided to pass and I will buy a Garmin Nuvi 885T instead. Its got a voice activated system, that according to reviews, actually works really well. It also has all the other features I want in a Navi but for WAY less that what the upgrade would have cost.
Hope that helps.