I am personally far from an expert on AC issues but I did post a similar question on the Ritter/Easley list. Nippondenso compressors can and do self destruct and cause "black death" from Teflon particles pushed throughout the system. The wisdom of the other list was that when a Nippondenso starts to make noise, time to consider replacing. They tend to go out after 150,000 miles.
The problem with black death is that you need to replace, not just flush, virtually everything forward of the firewall -- condensor, manifold, etc, so not a trivial expense.
Apparently MB is now selling rebuilt Nippondensos. Were this my car I'd save my pennies and replace the compressor, and not use it in the meanwhile.