How much for A/C compressor and PS belt.

A couple of weeks ago, I noticed a burning smell and the A/C quit working. I looked under the hood but could not find the answer. And the burning smell went away. Today I hear a tap-tapping and my Power steering goes away. So's I look and sure enough the belt, which I assume runs A/C and PS together, is broke. I also check the A/c compressor itself, and the pulley is stuck. I will assume I will have to replace the compressor first and foremost(along with related freon evac and replenishment etc.). What price range will I be looking at, with labor and all? Can I drive my car without the belt without doing damage? Is it possible for someone like me, a sometime shade tree mechanic w/out much knowledge, to replace the compressor myself? I heard sometime back that there is an environmental friendly freon system installed in some cars such that a freon license is not necessary. Not much knowledge but I think I have good mechanical sense. So whaddya think?

Now I've got 2 quotes for the job. Both from mechanics that I've used and was satisfied with. One says $800 and the other $1200. What's the deal? How can there be such a difference in cost?