i changed my fluid and my moan pretty much went away. I sucked out the reservoir with a turkey baster, refilled, started engine, turned wheel a few times, shut off, and repeated about 5 times.
Someone put ATF in there, it was a nasty color and it made a horrible whine. I replaced the fluid with Prestone power steering fluid, says it supposed to stop squeals (red bottle, got it at walmart)
Probably not the most efficient way to change fluid, but it was easy, and i wasn't worried about introducing air into the system, since i was only emptying and refilling the reservoir.