I would definitely at least change the cap and rotor since they’re cheap. Just gently wipe off the rust dust with a clean rag or paper towel. I personally wouldn’t add any gunk-- the contact cleaner shouldn’t be necessary because you just changed the cap and rotor and the WD40 shouldn’t be necessary because the cap should keep any moisture out. The only “product” I might consider would be to blow it out with compressed air (while wearing a mask!).
I agree with Busted that there is might be a distributor replacement in your future, but if that dust has had the better part of 20 years to accumulate, it might not be anything to urgently worry about. I would just clean it up, do the cap and rotor and then check it again in a couple thousand miles.