The Liberty has a button on the dash, it's a single momentary button, when 12v is provided on that wire to the control module, it turns the system on, and then again on the same wire, it turns off. Easy enough. This button also has an indicator light in it to tell you when the system is on, you may want to replicate that somewhere.
The stalk on the steering wheel has 3 functions. Accel/resume, Decel/set, and Cancel. This is done using a 12v momentary pulse on 2 wires. There are a couple diodes in the switch so it provides 12v to both wires simultaneously for the cancel function (see attached). You could make that your 4th function by replicating those diodes, or leave it off (easy enough to touch the brake pedal to cancel or turn the system off).
I assume the switches are from an EA81 sedan or wagon. I don't have any good diagrams on the function of those, but again, shouldn't be hard with a multimeter to figure out how they function and apply a power source to one wire and get it out on another wire when the switch is pressed.