It is my pleasure to be able to help in this forum. I love my van as she have gave me so many hours of pleasant driving time in long trips.
Your Nissan dealer will help you 100%. Just be ready for the hit. If they have to replace the thermo-element, I can see they will easily charge you a minimum of two hours plus the part. If it is just adjustment, it should be less or equal to 30 mins of labor.
I noticed that my van take more then two minutes to go from high RPM to normal operating 750 RPMs. Yours should be about the same. I am in Houston and you in Miami. I believe the ambient temp is about the same these time.