307 Data bus

Has anyone here interface a PC to the 307's wiring bus to be able to read data such as RPM and speed?

I have been looking around and know the the car is wired with multiple CAN busses

and would like to avoid having tobuild my own CAN-Serial device if someone knows of anyone selling such adevice.

I found these

but at $800 thatsway to much for a bit of fun project. I would imagine in the end I will endup knocking something together with and AVR or something simlar. Also if anyone knows a list of command codes and protocol format that would be a big help aswell!

Thanks

Stephen.