I may be entirely wrong, but I can't see how autofocus between completely different manufacturers equipment would be possible unless compatibility was built in from the ground up (not likely between any body manufacturers). I suspect the autofocus firmware in the Panasonic body would need to incorporate Nikon lens routines, and they'd have to be licenced by Panasonic, but I doubt nikon would license that kind of thing.
Happy to be corrected tho!
As for the M42, does the lens not have an aperture ring you can use?