I also have a 160SR and the fan belt is also squealing on my car. I use a silicone spay... then its quiet for about 15 days or so.
I have heard from a Nissan mechanic, that many of the K12's came with a bad fan belt when new... some kind af manufacturing fault. He said that he has changed alot of these belts.
I dont know how hard it is to change, but I looking to get mine changed soon.