I just spoke to my long time indie mechanic...he has rebuilt dozens on MBs...order the rebuild kits, new brake lines, pads and rotors.
My two cents, which you can toss away if you like.
When you send brakes out (either to a reputable brake rebuilder yourself, or through a local foreign auto parts supplier) the brake caliper is put through a very standardized rebuilding process which ensures that everything is done to specification.
If all you do is brakes, you do them exceedingly well. The same holds true, as an example, for factory-rebuilt Bosch products such as alternators and starters. There's a process they go through to disassemble, and rebuilt the parts to new quality. That's not to be confused with cheap rebuilts done in some third world country with Bosch parts--I've heard there are some disasters in that realm. Lastly an engine rebuilder such as Metric Motors in the USA or Crewe Engines in UK goes through a process honed over years of engine rebuilding experience that, frankly, an independent can't touch. An "indie" may have rebuilt dozens of calipers, but that's inbetween changing oil, changing tires, flushing cooling systems, answering the phone and what have you. The rebuilding process is generally done in better controlled factory settings. Before you dismiss that, take a look at the details in the links below.
Also, consider the cost. When I was searching for restoration shops, one shop provided me a detailed example of what he did for a prior customer which included a detailed list of what it took to rebuild the starter and alternator. I can suggest that at the hourly rate of most mechanics, the cost will exceed a proper rebuilt unit. If I did the math on that rebuilt alternator and starter it was several times more costly than just buying a factory rebuilt unit. The cost of a caliper rebuild is probably in the $75 each range, inclusive. That's about the price of your parts alone, right?
I've seen several restoration projects bogged down beyond belief because the mechanic and restoration shop insisted on doing it all themselves...instead of intelligently sub-letting work where it made the most sense, usually on items such as those mentioned.
I'm sure also, that Metric Motors has many a horror story of engines being sent to them that were started by others, but given up on for one reason or another--including those started by independent mechanics that just got bogged down in too many things to focus on the proper rebuilding of an engine.
Here's a great link to a UK caliper rebuilder:
http://www.brakecaliperspecialists.uk/brake-caliper-refurbishment/ They have a "do not try this at home" mantra, but do offer some guidance to those otherwise unpersuaded!
Two USA suppiers are the aforementioned Goldline Brakes, and Phoenix in Chicago.
http://www.phoenixcaliper.com. Also, White Post in the USA does it with SS cylinder wall relining.
http://whitepost.com/brake-sleeving-rebuilding-services/. I will have my calipers rebuilt this summer, but I'll probably just take them to All Euro, a local place that has carries all OEM ATE parts, but can send the brakes out.
http://www.alleuro.com. They will come back quickly.
More on "process":
http://mercedesengines.net/about-us/ and
http://www.creweengines.co.uk/remanufacturing_engines_process.htm