Navigation retrofit ??

It would cost several thousand dollars and much work to do it. You would be better off going to an aftermarket unit.

I haven't heard of anyone doing this. I don't think you could get a dealer to install the system. It would require replacement of many wiring harnesses, dash parts, installation of sensors, etc. I feel sure you could trade the vehicle in on one with the nav system for less money than you would have to spend to retrofit the system.