I don't think that it's possible to "trade".
Since the GPS hardware is already installed in all FiSTs (nav or not), what makes the ones with the Navigation option different is that the software (maps, etc.) is factory installed. To my knowledge, not even the dealers can alter that.
Since the GPS hardware is already installed in all FiSTs (nav or not), what makes the ones with the Navigation option different is that the software (maps, etc.) is factory installed. To my knowledge, not even the dealers can alter that.