How to replace power steering pump? on 1997 Cadillac DeVille

Cadillac was making a noise. I took it to a mechanic and was given a price of $500-$600 to repair it. You can buy the part online (reman) for less than $100.00. This car looks like new and I do enjoy the ride, but repairs are so expensive I don't want to put a lot of more money into it, as I plan on selling or trading it.

Asked by for the 1997 Cadillac DeVille
Sell it. Most of the estimate you got was for labor --not the pump.
I took the Cadillac to another garage. Three of their mechanics looked at it and listened to the noise and concluded that the power steering pump did indeed need to be replaced. I let them do the replacement and the car was still making the noise. Then they said the alternater needed to be replaced. They replaced it and the noise is finlly gone. It wasn't the power steering pump after all. They left the new power steering pump in at no charge, but replacing the alternater and serpentine belt was an expensive repair.