It's possible, but why? You'll have to invest a lot in dashboard part changes, new interface controls for the AC/heating and new dash mounts. That's a lot of work and possible money for that.
A much easier and probably cheaper way to go would be to install a new head unit that incorporates nav. It's a lot less work and requires no dashboard changes. Plus you get Bluetooth connectivity and all the modern connections for todays mp3 players and phones.