Yashica jis tools

Yashimo, I think you will have BIG problem converting your lenses to a Nikon mount.  The registry distance is in effect a negative one, so you can't get proper focus. 

Having said that, Leitax does offer a conversion kit for some Zeiss MM lenses although it will require removal of many components from the original mount and hacking some of the rear baffles as well.  Other than the sawn off baffles, Leitax claim that the process, if done correctly, is reversible.  I don't know if some or any of the Yashica ML/DSB lenses will work with the same process - it may be worth enquiring.  They do however show the dismantling process on their pages which is pretty useful and, if you use C/Y Zeiss lenses, some pretty powerful endorsements of some of the MM glass.

As to tools, you will certainly need a set of professional quality JIS screwdrivers - the sizes I use most often are #00, 2mm and 3mm. The screws that hold the bayonet mount are glued so you may need to apply a lot of pressure and being of soft metal, a cheap screwdriver will destroy the cross-heads so be very careful!  You will also need a good quality spanner wrench with a variety of heads - the curved ones are particularly useful - if you need to remove the rings and baffles that hold the elements in place.  You will also need a set of rubber rings to help with removal of the front bezel/nameplate on many lenses to allow access to the front element groups and/or the aperture assembly.  You may also need some helical grease and I use MicroLubrol's HELIMAX-XP which does the trick - there are quite a few helical greases out there; the key is to ensure they do not contain oil that can leach out over time.

If you ever wish to repair damaged filter rings or metal hoods, then a good quality lens vise will often do the trick.

Finally, you know the obvious imperatives - a clean, dust-free environment; lint-free or latex-type gloves; plenty of light and even more patience....   And if you are removing a light attack of fungus, I use Pond's Cold Cream and isopropyl alcohol.

The total cost will about the same as buying a ML 50mm 1.4 but it will pay for itself if you buy a few lenses 'for repair' and then bring them back to life and sell them.