You really need an air conditioning specialist to do a proper overhaul of the system, replace whetever need replacing and convert it to modern refrigerant. It won't be cheap in the context of the market value of a normally-aspirated Lux, which is why most people don'lt bother. I'm planning on getting myTurbo done next year, and am expecting a big bill.
I can't recommend anyone from personal experience yet but this link...
http://www.air-conditioning-installers. ... allers.htm ...may help you find someone local to wherever you are