Nissan Repair: 1998 Altima Timing Chain, timing chain cover, nissan altima

Question
I have a 1998 Nissan Altima with exactly 150,000 miles on it.  I have noticed a high pitched whine from the engine when it idles for a few minutes.  I think this may be a loose fan belt but I'm not sure.  The owners manual doesn't mention anything about replacing the timing chain.  The dealer said the chains should be replaced at 100,000 miles which I don't believe.  I can't find out any information on the timing chain. I've owned the car since it was new.  

Answer
Matthew,

The high pitch noise could be the alternator or one of the belts.  If you have not replaced them recently this would be a good time to do the belts.  The timing chain is usually a run to fail item and when it stretches it will make a grinding slapping noise in the timing chain cover.  You will know what that sounds like...  So, if it were me I would replace the belts and while they were off I would hand spin the alternator and see if the bearings are going out on it.