Well, congrats on getting her started again, although I wouldn't say replacing the CPS was the easiest
I would have thought the rotor swap would be right up there with "easiest"!
One thing about the XJ40 rotor - don't think of it as part of a "replace cap wires and rotor" routine as you would with any ignition system of this type ..the rotor on the XJ40 is somewhat
unique in construction as it doesn't have a solid brass top section but a two part affair that uses an electrical component potted in epoxy to bridge the connection between the coil connection at the centre and the business end that distributes the spark to the various plug connectors inside the cap.
This electrical component can and does
fail, causing erratic running or idle as it begins to break down.
Eventually this will lead to total complete failure with an open circuit and a no-start condition. Just this summer I was immobilized by this very problem so the car had to be flat decked back home. I didn't have a spare in the car, my spare was in the garage.