I know this is a problem on many aging cars...but what is the general solution?
Change the PS pump?
Change the belt?
Change the fluid?

btw, it whines when cold.

 

step #1 is to change the fluid and see what happens.

usually the whining noise is caused by air in the fluid when it goes through the pump.

easiest way to change the fluid is to pull the hoses off the reservoir tank, and stick the "suck" hose in a new bottle of ATF or power steering fluid (ATF will work fine, Recommended by nissan).. then put the return line into an empty container, then just start the car and turnt eh wheel from full-left to full-right a few times to be sure it's flushed completely through.
then reconnect the hoses and refill the reservoir to the correct level and you're done.
I don't know how much fluid this will take.. I'm guessing 2-3 quarts, but I haven't actually done it myself to tell you.

 

Thanks Matt...I'll add this to my list of DIYs.

 

all i can say...messy job.