Whining noise in area of power steering pump. Replace or flush? It's a 2008. Probably never been changed. Bought used.
If you're getting a "whining" sound it could be as simple (and easy) as low or degraded PAS fluid. First up: check the level - if it's low then that's a pretty telling give away. If not then it's likely worth changing the fluid anyway just to rule it out.
If the fluid hasn't been changed (or you don't know how long it's been!) then I'd go for a full flush change.
It's possible though that the whine is the beginnings of the pump failing as sometimes the bearings sound like that on the way out. But I'd worry about crossing that bridge if you get there.
If the sound is more of a squeal or screech then the belt is the more likely culprit (assuming your car has a belt-driven PAS pump)
Let me guess, it's a Ford, right? Add Fluid Like this, and Tell us if it goes away:
Take the P/S cap off (cold)
Fill Fluid to max cold level
Turn vehicle On, Watch to see if the fluid rises or falls from your fill level. Add more fluid if it falls.
Move your steering wheel hard left and right to work the system. As you do this, occasionally check the P/S resivour to see if there are air bubbles (foaming fluid)
Once all the bubbles are gone, the fluid is heated and slightly below the max hot line, install your cap.
If the noise doesn't go away, you need a pump, air in your P/S system kills those fragile pumps of yesterday SO quickly. Especially if it's a Ford!