I guess you need to power it up in the vehicle and listen on the CAN bus to try to work out what messages are required. Do you have any physical access to the MS-CAN bus in the vehicle? (On my Mazda 3 it is available through the OBD-2 connector). In my car the pins used for MS-CAN are not the standard CAN pins so I couldn't use a commercial OBD-2 tool. The cheapest way I could find to listen to the CAN bus is with a Microchip CAN Bus Monitor Demo Board. The provided software is enough to listen to the messages.
You can also use the provided software to send messages, but if it's more than one message you'll probably want to write your own PC software to do this. The protocol is not too hard to work out, and I have already done this. The challenge is writing USB software in general - I used libusb under Linux and there is a Windows port so perhaps it wouldn't be too hard? But this depends on your coding skills.