Power steering fluid or the pump itself?

Ok i got a little problem that seem to be coming from the power steering pump.

When the car is cold and i turn the wheel full left or right , everything is perfect,no sound.

But..when the car gets hot,in normal temp range if i turn the wheel full right or left the pump make a howling noise.

So what should i do? Replace the ps fluid with brand new one or i should replace the pump right away?

How hard is it to change this part?

Thank you ;)

Anyone :confused:

Is the resevoir low when its warm check that. if not i would say it is the pump but changing the fluid is the cheaper alturnative if you want to start with that. Changing the pump isnt really that difficult just time consuming. Also make sure to check for leaks and such because believe it or not a leak or restiction can cause a PS pump whine also.