I have been looking into this HEX-CAN, and all i can seem to find, is some expensive device, but I have also found a few bits and pieces about projects, where people read and write data from vw cars, without any specific mention about “HEX-CAN”.
This situation about it being hard to find detailed information, is quite common for CAN-bus, OBD2, car-debugging etc.
Do you have any more information you can send me?
Regarding being able to control it from the steering wheel, you can listen to/snif the can traffic using the autopi dongle, to identify which messages are sent on the CAN BUS when you click the buttons, and then setup the dongle to trigger actions when it sees these messages. This of course depends on the steering wheel functions being connected and controlled via the CAN bus (which it should be).
Regarding the display, this is entirely dependent on your infotainment system. The dongle can send various commands, so if it’s supported, you’d need to find out what commands to send.
Check out this project: Mazda Infotainment + AutoPI [Idea] I think he is planning to send commands / messages to his infotainment system. But it is an entirely different car, so although you most likely can’t use anything directly in your project, maybe there are useful info anyway.