Since a few weeks, I have a nice old 1988 F150. Actually, it is my first car and Im having a lot of fun with it, driving and finding out how everything works.

The drive belt makes a pretty anoying squeaking sound. First thing I thought of was that the thing was just worn. That is not the case: It looked pretty new (surprisingly), and also the automatic tensioner indicated that is was within the 'good' range. Also the it was pretty tight.
The previous owner confirmed that it had not run 5000 miles. He solved the sound by spraying some WD40 on the belt so now and then.


(1) I was wondering: Is it necessary, and anyway a good idea at all to lubricate the drivebelt??
(2) The A/C system is completely empty (when turned on it smells funny, I get water(vapor) in the car at the passengers side). Could this cause the sound somehow?
(3) I'm affraid that the bearing of one of the pulleys might be worn. Is this wise to check, could it be dangerous?
How to check that?