Leitz V35 Enlarger

I have acquired a second V35 the first one that I have is mint, but has a couple of niggles, like the masks don't work, and the second one has very tired plastic and some other issues, but the masks do work, does anyone have any experience of swapping the negative stage? Any adice gratefully received. Also I would like to refresh the white plastics on the arm, any suggestions for a cleaning product, they have gone quite yellow. I would like to restore the tired one but also improve the mint one.

Any help please. TIA

For the yellowed plastics, look up "Retrobright". It's basically putting yellowed plastics in hydrogen peroxide and exposing them to UV light. There are lots of different ways to do it (gel vs immersion, sunlight vs UV lamp, etc., etc.). It's a technique used commonly by retrocomputing enthusiasts to restore yellowed plastics on old computers and game consoles.

Thank you, I went the Hydrogen Peroxide route.