I don’t have an answer about the OEM GPS system. I saw it a few years ago but don’t remember if it is removable. At any rate, I suggest you investigate the Garmin Street Pilot III system. Garmin is at
http://garmin.com/ and there are a lot of reviews on the device. The street Pilot is at
http://garmin.com/products/spIII/ It is generally considered excellent – far improved over even the current MCS based GPS system. And less expensive than the OEM GPS. Also in the near future (in fact already done in some systems and areas) the GPS devices will incorporate real time traffic information to help route you around traffic jams. And, BTW the Garmin is removable.
Regards,