I had this done last year but I took it in to an independant guy. He converted the system to R-134. Is that what you have? R-12 was going to cost more just for the gas than it was to convert and buy R-134, and pay for his labor!! It was going to cost about $90 per pound of R-12, whereas R-134 is about 25 percent of that.Worth thinking about if you are still on R-12. I would not do this myself, as it is a bit beyond my capabilities, as I dont know too much about AC systems. You might feel more comfortable with it.