Today I bought a r-134 retrofit kit for my 420 sel. the car has a Nippondenso compressor. The kit came with three fittings (two red and one blue) two caps and some ester oil compatible with r-12 and r-134a. What should I do next, I don't have the proper equippement to clean or charge the system. Can I change the oil myself, where to put the fittings and what should the shop do on the car?