The conversion, as already noted, is much more than changing out the coolant and a few valves. Stay away from the "over the counter" kits. I would have it professionally done as many major components will need to be replaced with new ones, the system needs to be airtight, everything working and pressurized correctly, etc. Your compressor might need rebuilding or replacing, who knows at this point
Most shade tree conversions never turnout working correctly
