I tried to do the same thing with a Journada, I asked the question on the tech log a few months ago and was pointed to an Ausie side where the software to do that is provided (demo version). I still havn't had enough time to play with it yet, if you do a search on GPS, I'm sure you will find it.
Wouldn't mind a pin-out diagram Mark1, if the offer is open to all>
This is the URL to the Ausi Site.
http://www.powerup.com.au/~lornew/oziexp.html