I think that CAN-BUS Shield I linked has an Arduino library on Github, complete with examples you can reference, when you're ready for that step. You mention that most of your dev experience is in ...

The functionality can be added via 3rd party modules or through manipulating the car’s programming with some prepackaged software, but [Igor] wanted to give it a go himself.

You can engage in this kind of dialogue with a non-CAN bus electric actuator, but it requires more external switches and wiring. You can also engage with a hydraulic cylinder, but it is a far ...