2016 Nissan Maxima (166k miles) - CVT fluid is very black but no symptoms. Safe to do a drain & fill?

Hey guys,
I have a 2016 Nissan Maxima with 166,000 miles. I recently replaced the CV axle on the car, and while doing the job, I noticed that the CVT fluid that came out was very black.
The car currently has absolutely no symptoms: no whining noises, no jerking, and no slipping. However, I suspect the transmission fluid has never been changed by the previous owner.
Since the oil is heavily degraded, I want to address this immediately, but I know how sensitive Nissan CVTs can be at high mileage. I am planning to do a simple drain and fill (absolutely NO power flush).
My questions for the mechanics and owners here are:
Is it safe to proceed with a drain and fill given the mileage and black fluid, or am I "rolling the dice" too much?
Should I replace the external paper cartridge filter during this first service?
Since a single drain only drops about 4-5 quarts, would you recommend doing a second drain and fill a couple of weeks later to gradually clean it out?
What are your thoughts on dropping the pan to clean the magnets/internal strainer with this mileage and black fluid? Or should I leave the pan alone to avoid steering up sludge?