I have no direct Nissan experience, but I do have some Subura experience that is somewhat pertinent.
Fluid in most modern sealed CVTs is checked at the fill hole, with the vehicle level, running and the transmission in the proper temperature range. With the Subaru, that is an 18F (10C) wide range.
If you are not willing to work out some accomodations (To ascertain trannie temp) it is best left to the dealer. I used an IR gun for temp reading......So far, so good.
I also started doing drain and fills at 60k miles (Subaru said it was lifetime fluid, but has backed off that with time.) I plan to continue drain and fills at 30k intervals, after my third one at 90k.