What does it cost to replace AC in a 990 jeep wrangler ?
The AC system consists of many components. Your question is to vague. What component has failed?
All I know is that owner told me AC didn’t work- he has owned car for 12 years, didn’t think it was worth fixing, so I assume repair involved compressor and all- what would ballpark be, assuming max repairs ?
You need to look under the hood carefully and verify that there is a compressor, condenser, drier, expansion valve and all the plumbing pieces in tact. If it appears to be complete call a local McParts store and price the compressor, drier and expansion valve for a starting point.
Your Jeep orginally had R12 as a refrigerant. If your going to rebuild this AC system, get components that are R134a refrigerant compatible. R134a refrigerant is a lot cheaper and easier to aquire than R12 refrigerant.