The stepper motor is easy to access. It's on the right-rear of the intake plenum, and has 4 wires coming out in a square pattern. It regulates extra air going into the intake to adjust idle speed. Replacement is easy, it just unscrews and undo a single wiring connector. I believe new ones are available from NAPA and a few other parts stores, it's not a Rover dealership only thing.
Checking the base idle is easy, when the engine is warm just look at your tach. If your engine idles higher when it's cold, and drops down to normal when it's warm, then the stepper motor is most likely working fine. Just reset the code and see if it comes back.
The continuity testing basically means to check that the wires and connections to the computer are ok.
Part of the system is the vehicle speed sensor, attached to the transfer case. Again, it just reccomends testing the wires for continuity. Haven't done anything with the VSS yet, so can't make many comments on it.
My oil line fix
My 100k stopped odometer fix
Brace for impact, I'm in a "modifying mood". Massive thread count inbound.