Something I learned was that you will probably have to make tools, unless you have a really good optical wrench. Fortunately tricks like filing down pliers to make very small tips and filing in-between cheap screwdriver flats work really well. Years of SMT work finally paid off as some cameras require desoldering certain parts to get into the depths. The biggest risk is scratches where the OEM tooling otherwise fits perfectly, but I'm not that prissy over a 50 year old SLR. The repair guides from the manufacturers are pretty opaque and serve only to show where things go. Often they list tons of bespoke equipment and calibration tools that you won't have.

Sadly it seems a lot of Nikon lenses were not designed with reducing focus shift as a priority. That completely wrecks them near their minimum focus distance on film bodies. Phase-detect AF only sees light coming from the f/5.6 direction so AF will systematically miss its target at any aperture with a different focal plane. There is no live view on film, obviously, so no on-instrument way to correct it.

I am going through this right now... I really wanted an 85mm 1.4G but according to reviews it will put focus completely behind the subject from f/1.8-f/5.6 when closer than head+torso distance. In headshots if you target the eyes it will focus somewhere on the temples. I have no idea if it really matters in real life. So I am stuck with the 1.8 G.

Edit: A focus screen with some kind of prism mechanism would let you manually focus, at least, by holding down DOF preview. Richard Haw describes cutting down and shimming off-body focus screens so it's possible. Actually now that I look it up, whoa, an off-the-shelf one exists on aliexpress ("Dual 45 degree Split Image Focus Focusing Screen for Nikon D1 D1H D1X F100 PR129")