I once wrote about this on the old NG.com a long time ago but did not find the post any longer. The 45 PC-E is the easiest of them to modify, only some new flat cables needed. The 24 PC-E is the next one, it might need one cable more or something similar. And the 85 PC-E is the most difficult. It requires some extra parts also to prevent light leaks. I'm not sure if I remember right but it could need something like 12 parts in the modification. I ended having the 45 mm lens modified. But it was not a good solution for everything. Many times I wished I had not modified it.
The Nikon repair shops have a list of the parts necessary and they can do the modification without damaging the lens. I would not try it myself. (the old 85 PC is a different thing, it is easy to modify, no parts needed). The required parts are the pricey part, and one needs them anyway.
-Jukka-