and how much does it cost to replace receiver dryer and expansion valve and recharge the AC system 95 E320?

This morning I brought my car to a local MB shop in Northern Blvd Queens New York to fix the AC. I told a lady there that the AC is not that cold and I told her to find out what the problem was and tell me at work before doing something because I had to leave the car at the shop.

Before I left she told me that it would probably be a leaking or I had to replace something that was broken and would cost me around $280.00 for the parts.

When I picked up the car I was shocked because they charged me $638.63. I asked the lady why it cost that much. She told me that the labor to perform the job was 4 hours and they needed two people to do the jobs. I looked at the sheets and find out they charged me $356.00 for 4 hrs labor and $282.63 for the parts.

I do not mind paying that much but I really doubted that they really spent 4 hrs to install receiver dryer and expansion valve and recharge the AC system or maybe I am wrong.

Does anyone know how long it takes to do that particular job? Does it really take 4 hrs?
I would really appreciate for any input.
Thank you.

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1995 Mercedes Benz E320 Special Edition
Spruce Green Metallic /Parchment.