I don't know why you guys are removing all that stuff, I changed my belts last night and did not even touch the fan or the shroud, the belts can fit over the fan you just have to fit it of a few blades at a time, yes i removed the skid plate, but man I don't do all that work. By the way our xterra is a V6 if that makes a difference.
By the way i saw a question about the alternator belt.....you don't have to fit it over the fan, just do all the work on that belt from under the car, you can fit it on the crank pulley and the alternator.