Well, I'm almost wondering if you should get the gauges off ebay, and buy your own duracool and it it yourself. I wanted to just buy it once, and then I can change the charge whenever I like. Buying your own tools should actually cost you a lot less then taking it in and having it done. Read my post that I gave last year. Oh, and buying this DVD will be a great starter on how to do your own system:
http://www.autozone.com/servlet/UiBr...ENOW%7C%7Etrue
I think the only thing you might have trouble in, is finding a vacuum pump. I bought a venturi vacuum pump from ebay that runs off a air compressor, but it needs to be a pretty beefy air compressor. Of course, you should always rent a vacuum pump for cheap, and you only need to do it the one time to purge your current system.