Hi chris -- this forum is really powerful regarding Contax lens users:
www.mflenses.com
-- honestly ! I have got some Contax lenses (I use Canon adapt -no problem) in my possession and I discuss some questions on this forum..
1 - C/Y to Nikon mount -- that's a question for this forum: www.mflenses.com
2 - 'Oly' lemses on Nikon -- short discussion regarding possibility to use 'Oly' lenses on Nikon DSLRs:
Contax certainly cannot be used on Nikon via adaptors. IIRC neither can Olympus.
Nikon F mount is unsuitable for adaptation due to the long register (sensor plane to mount flange distance) and average throat (inner diameter of the mount flange).