Oil cap off

I have a 1991 honda acoord ex that I recently had taken in for an oil change. The attendent didnt put the cap back on. The normal mess happened oil on the bottom of the hood, engine, and headers. I knew the smell of burning oil is ok due to the oil on the various parts of the engine. I however found that the serpentine belt was breaking down and that the power steering was sluggish. If I was parked and I turned the wheel all the way to the right or left the idle fell from about 900 rpms to about 700. There is power steering fluid. There is no metal shavings in the oil so I am not worried about a crank. I am however worried that the belt and idle is high. Could there be something wrong with the timing of the engine? Or could there be something as simple as changing the serpentine?