I have a long standing discharged R12 ac system. I want to charge it with hydrocarbon refrigerant to check it. If I decide to have it recovered after recharging it is the shop liable in reporting it to the EPA?
More importantly, hydrocarbon refrigerant can be used in place of R134a without components or oils having to be changed. Since your system is using the old R12 permanent damage will occur. The entire air conditioning system needs to be flushed. The accumulator and orifice tube replaced before changing over from R12 to Hydrocarbon or R134a Refrigerant.
With your system being as old as it is you are most likely looking at needing to replace the compressor, accumulator and orifice along with flushing the system and replacing the o-rings. This is at a minimum.