I have read you cannot just insert the SD card to make the nav work. I also read Ford, or the Nav company, maintains a 'whitelist' of nav systems with paid-for nav capabilities.
I am not certain of anything here, but I believe I read (I'm on a lot of fora) you can get your serial number (or MAC address, or whatever the identifier is) whitelisted by paying the $795.
I bought the max package so I have not done any of this myself, but I think it is worth a call to the dealer (who may not know) or Lincoln support to see if you can pay for the nav and get it. It really is all about the $$$ so I don't see why they wouldn't be glad to pick up an easy $795.