Problems with vacuum pump leaking

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I have had the vacuum pump replaced, a year later(3 months ago) the valve cover gasket replaced and now am being told I need another vacuum pump. The dealership wants $960 to replace it so I did not have them do the work. A week after picking it up from there I get in the car drive a mile the oil light comes on and the engine was making a winding sound so I pulled over cut the car off and checked it and there is no oil whatsoever in the car. I had to put 5 qts in it, it started back up fine but I'm at a loss for where all the oil went. There's no oil on the ground where I park at home or work either.