Hey, jmcdonnell
I am EPA certified in A/C repairs there is no consequence in using a retrofit kit from Wal-mart or Auto zone. Keep in mind that you do need to evacuate your system, TAKE IT TO A PROFESSIONAL!! so that they can check for leaks and pull a good vacuum do not take apart any lines or vent the refrigerant (r-12). Last I knew the penalty for releasing any type of refrigerant into the atmosphere was $27,500 and a reward for turning somebody in for releasing ref. was $10,000. Just to let you know I replaced the Compressor, receiver/dryer, and the orifice tube earlier this year and used a retrofit kit to fill it up. I beleive that high side pressure was approx. 200 psi and low side was around 35 psi. It is still blowing cold air, not that I need it right now.