I'm with DOC on this one. Some of us are proud of our diyer skills, but "wondering" just how good a job I "may" have down rebuilding brake calibers/master cyls. isn't something I care to wonder about.
I looked into MB guaranteed rebuilt calibers a few yrs. ago.
This MB shop, located on the west coast had the best price I could find. They may have a similar offer for what you're after.
http://www.caliber.mercedescenter.com/mbcenter/b/services/serviceparts.jhtml