Swapping wheels: 2017 Platinum 20" for 18"
 

I'm interested in swapping the 20" wheels from a 2017 Pathfinder Platinum, for the 18" wheels shipped on lower trim levels. I want to soften the ride.

Is this feasible? Any risks or problems to watch out for? (Of course would switch to higher-sidewall tires so road-contact diameter doesn't change.)

Any estimates of what this would cost if I went through a dealer?