I remember reading about this in the manual but i don't have the guts to try it! 
The update for the head unit. I've been having some connection issues with Car Play and my Iphone so I thought that maybe Nissan addressed that but it may have been just my USB cable to car USB input.I just remembered, there are two update options for OTA updates. One for the head unit, and one for maps. Which one are you looking to perform?
What year is your Murano?I have checked several times for HU OTA updates but there has never been one. I think some of the updates are very large and are likely limited to install at the dealership only.