There are many web sites which provide info regarding A/C conversion. Learn more about it before you start. Here is one of them:
I went to one other web site (forget where) which had one page info about older MB conversion. As Chrisg above said, there is not much to change on a MB. I recalled that a new higher rated pressure switch was recommended by the author. He also stated that the conversion on older MBs were not as good as other conversion due to MB's poor design of the A/C system.
If you need a vaccuum pump (not the engine vaccuum pump on a diesel engine) to service your A/C system, you may conver a good compressor from a discarded refrigerator (that was what I used in the shop back in the old days before all the new laws came up). Some compressors work very well as a vaccuum pump.
You A/C system went empty within few days. You had a big leak and it should be very easy to find. You saw a lot of oil on the back side of the compressor. That might be the leaking area.