This is a great topic, and perhaps a subject that other readers will want to address.
The first priority for me is the dial, followed closely by the case, for the following reasons. In my view, the dial is "everything". I can tolerate some wear or degradation of the dial's finish, if it occured naturally. If someone has attempted to re-touch or re-paint (excpet maybe luminous dots), then I lose interest . . . end of the discussion. Somehow, I just can't force myself to wear a refinished dial.
On these black PVD Monacos, the case is the next priority. Anyone can take the case from a blue 74033 Monaco, and have it PVD coated. But to me, that would not be the "original" watch . . . it's a different piece of metal on your wrist . . . it is a re-cased watch. If I have the original dial, and the original case, then I feel as though I have the core of the watch. So this one passes the test.
Next up are the hands and needles . . . in this case, a bit of a bummer. Still, needles and hands of the precisely correct shape and size should be available, so with a little custom-mixed orange / red paint, this one will look good. It won't be entirely original, but it will look correct.
Next rung down are the crown and pushers. Nice if they are original, but given the daily wear and tear, and the fact that this ia a manual-wind watch (with daily use of the crown), there is little hope for originality (if the watch has been worn a lot). So there is also little "damage" done if these parts are replaced with the correct pieces.
Last up is the crystal . . . original is nice, but there is almost no hope that this will survive well, on a watch that is being worn for 30 years, on a regular basis.
That's the quick run-down . . . Sorry that we didn't get to the movements (entirely original versus parts replaced), but that can be for later. Thanks for suggesting this excellent topic for discussion.
Jeff