I 2nd (or is it 3rd?) stay away from rebuilt compressors! They are garbage. We refuse to use them at my shop because of all the combacks. New only.
We have used the Compressorworks that Artifficialist doesn't like and never had a bad one. But these are new only.
Also as stated you must flush and clean the entire system if it's contaminated, replaceing the condensor is usually mandatory and always a new dryer.
No shortcuts in AC repair.
I'm a DIY when it comes to AC repair and this is such a true statement. I learned this the hard way.....twice.
I think most if not all issues with DIY AC service comes from two or three places:
1) Not enough lubricant in the system. Without a full flush and clean (essentially starting with a "dry" system), you never really know how much lubricant is in there.
2) Undercharging. The system needs enough refrigerant charge to be able to carry the lubricant throughout the system.
3) Use of canned stop leak. This stuff is NO GOOD.
Here's a link to a very helpful forum. Just a few minutes of browsing some of the posts will make it very clear if you're attempting something that could get you in over your head in a real hurry. Don't get hung up on who sponsors the Forum. There is very sound advice there.
http://www.autoacforum.com/