800 RPM sounds about right. I don't know exactly what your problem is. When you turn the AC on idle goes up? That's normal, the AC compressor puts the engine under load. When the car senses load it raises the revs to keep the car from running rough.

A vacuum leak would cause a high idle. Is that what your problem is? Or does it fluctuate? Are your spak plugs new? How about the rest of your ignition?

If you're just worried about idling @ 800 RPM then turn the idle screw to adjust it. Sorry I'll need more info to help more thoroughly.