I have a ~1990 Cartier in for service right now, and the watchmaker at the local Cartier boutique has indicated that rather than try to fix the problem (running ~2 minutes a day fast, and the movement is pretty well dried up is what I am told) he recommends replacing the entire movement with the up-to-date calibre. Old movement was a Piaget 9P2, new movement a 430MC from Cartier which I understand is actually the same as a Piaget 430P, or at least one is based on the other (still unclear to me).
My question: am I committing some grave sin, damaging resale value by going ahead with this service? This is only a secondary concern for me, as the watch has considerable sentimental value to me and I have no plans on selling anytime soon. But never say never, and i wonder if the watch is doomed to suffer an ignoble death at auction in 4 or 40 or 140 years because of the movement replacement I'm contemplating today.
So, for a mid-range dress watch like this, is it no big deal to have new movement installed, or does replacing the original movement make a major difference to resale value?