How easy is it to get a Rasberry Pi to interface with CAN-Bus equipment? How expensive?

I recently stumbled across one of these out of a newish mazda: http://imgur.com/bm0zXQW - the big center dial +surrounding buttons is a module. On the back of the module is an 8-pin connector in a 4+4 arrangement.

I think the dial would make a fantastic volume control, plus it can be depressed to act as a button, offers at least 4 (i think 8) directional points and of course the surrounding buttons. I'd like to hook it up to my computer at work to control volume and maybe some other stuff to. If possible I'd like to do this in a cost effective way. Sure its great I got the part for free but if I spend $100+ or literally months making it work then it isnt a very attractive project.

This leads me to my question(s): How robust are the CAN-Bus drivers/software stack for the Rasberry Pi? Would this be nearly plug and play or would the signaling be much more complex than I'm guessing it to be. Are there programs that help dump the traffic/signals received so I could work it out for myself kinda like wireshark?

I figure $20-30 for the Rasberry Pi (depending on which version I need) I'm not sure how much for something that can decipher CAN-Bus signals though. Some of the ($65!) modules look like they are for interfacing with the OBD connector more than generic CAN-Bus devices. I get that this wont be a single day project but I'm kinda looking for an excuse to fiddle with a rasberry pi/can-bus equipment anyways. I'm just trying to feel out the scope of problems I can expect.