CLK500Lo

I have a 2006 CLK 500. It has over 150k on it but it runs very well bc it was properly maintained b4 I purchased it from a prvt owner. One thing I didn't like was a noise it made whenever I cut the wheel to make a u-turn or simply park. I was told I needed a new P/S pump. I purchased a re manufactured pump and new P/S reservoir from NAPA and had my mechanic put them on.it drove like a dream the 1st day but then I noticed the noise was slowly coming back and the steering wheel was stiffening. I open the hood and see the P/S fluid leaking profusely. I couldn't get to any Auto Zone bc of my location at the time and the severity of the leak, so I went to a local gas station and purchased some reg P/S fluid in it to get me home and it ran and drove perfectly fine until I got close to home bc by then the reservoir was almost empty again. Took it back to my mechanic and he admitted he made the mistake of not putting the "O-Ring" in the reservoir. So he puts it in and reassembles everything. Now my P/S isn't workin AT ALL. I've gotten several diff assessments from diff mechanics.

1: Need new pump bc I was sold a defective one by NAPA

2: Need new pump bc the leakage didn't allow the pump to be properly lubricated and it fried on the inside

3: Need to buy a BRAND NEW pump bc re manufactured pumps always do this

4: Need to get a new electronic hydraulic valve (is that the proper name? What is that?)

5: Need to get my system flushed bc either there's an air bubble or the reg P/S fluid needs to flushed out of the car completely.

HELLLLLLLLPPPPP!!!!!!!