Yes, 350z parts are fine to use, I don't know about the fwd maxima.
Now, the only way to fix the plug tube leak is to buy a whole plastic cam cover, which is a pretty expensive fix. If you not talking about a lot of oil, and it isn't coming from the outside of the valve cover (that seal is replaceable), then it's best just to leave it alone. It doesn't effect any performance, as it's an insulator.