I'm not a tech, but I've done alot of research on AC systems and have repaired quite a few. Here's my advice. Replace the compressor, disconnect all lines (but don't remove them from the car, unless very easy) and flush each one individually. The flush I use is a terpene based (like terpentine) product made by Johnson. I do not use a flush gun, and instead, use a small funnel to fill each line, let the flush sit a while, and then blow it out with a compressor. Then repeat this until it comes out clean. Any suspicious hose/line should be replaced. Do not flush the receiver (replace it). Do flush the evaporator and the condensor. Replace all the seals. I have retrofitted systems to R134a and recommend it. You can use the appropriate parts from a 93 240, as it was an R134a system. I'm not sure, but I believe that year model used a more efficient condensor and evaporator to make up for the less efficient cooling capacity of the refridgerant. The R134a system on my 93 245 works great and is very cold here in Dallas. Whatever you do, don't open the receiver until you're ready to install it (last item in the system), put in the correct type and amount of oil into the receiver, and then immediately evacuate the system to a deep vacuum. Rent a vacuum pump that can get you down to at least 30 inches and keep it pumping for an hour. Then let the system sit for an hour and see if you have any leaks. When you recharge it, go by weight and not pressure. If you switch over to R134a, only use 85 to 90% of the weight of R12.