Steve,
If you really want to save a lot of money, get the R-134a Retrofit & Charging Kit made by Interdynamics Corp. They cost $34.95 and contain everthing you will need to make the change over. The kits contains full oil charge with "o" ring and seal coditioner, three cans of R134a, charging hose, and all the fitings you will need. You can get the kits at Advanced Auto Stores, Autozone or just about any auto parts store. Just follow the instructions that come with the kit.
I have converted two of my Mercedes to the R134a system with no problems. One conversion is five years old, the other is two. Air from the vents at high blower speed comes out at 38 degrees. Cold enough for me.
Autozone and the other auto stores also have reciever/driers, compressors and just about any part you will need to fix your AC.
Bill Lewallen Lexington,Ky. The Bluegrass State,,But the grass is really green, and so is our antifreeze..