it will be difficult to find any literature on it. prepare 2 quotes...1 showing costs now and 1 showing costs with clean up PER COMPRESSOR. make a point to discuss the down time. changing a compressor now is short and sweet versus multiple trips to change the oil and change filters which could increase the downtime. discuss what 'secondary damages' will occur such as lost product in the cooler/freezer, etc.
since it is a rack system, a failure of 1 compressor can damage the other compressors. keep in mind that some manufacturers require all compressors to be changed out for warranty purposes, but personally, i think that is garbage as long as you take the proper precautions.
Once you go black...you never go back to galvanized.