I'm looking for a factory navigation system for a 2006 lincoln town car?

Answer 1

A 'factory navigation system' is by definition installed at the factory. To get one, you have to buy the whole car.

If you want to install a system in an existing car, you have to install an after-market system. You can get one at a dealership or get one of the many advertised on TV, radio, etc.

It's possible that there are systems available on wrecks, but I wouldn't go that route.