Has anybody taken apart the HCH dashboard to see what kind of interface the MPG display has?

This is definitely a strange idea, but what I would like to do is create a system that interfaces to some part of my '04 HCH so I can read the current value of the MPG display and display it on a large (5" x 7") L.E.D. dot-matrix numeric display which will be facing out of my rear windshield. I'd like to show off my great MPG rating to all the people that drive past me on the freeway.

The dot-matrix display will be the easy part (I have done many microcontroller projects like this), it is figuring out where to connect to my HCH and what the protocol is that will be the hard part. I don't know if this is even do-able, because I am sure Honda does not publish a detailed Chilton's (or similar manual) for the HCH that goes into this kind of detail. I was thinking that maybe there is someone lurking on this forum that might have some inside information? I'm guessing that Honda uses some sort of CAN bus network inside the car. Does anyone know details on this stuff?

Stephen