You can remove the Sat Nav and fit a 'normal' radio unit, whether Ford or aftermarket.
You will need to change the centre dash console, the facia that houses the clock, hazard and screen switches (its larger than the std item) add in a climate control module and if fitting an aftermarket radio, you will need a facia adapter and loom conversion lead.
If you do decide to remove the Sat Nav, remove the boot trim to gain access to the DVD Rom, and REMOVE the sat nav disc before you disconnect the Nav touchscreen.
Hope this helps