Most everything I know about M110 motors
The M110 motor was produced for something like 16 years. Benz's longest production run I know of.
early motors had some problems with oil reaching all the necessary spots in the cam area, but that got fixed eventually.
There are plenty of motors available in junk yards. Lots and lots of them need rebuilding. Lots don't.
Rebuilding a benz motor is an experience very much unlike a pony, chevy or nissan (I've gotten my hands dirty with all 3).
All the parts you could possibly want are available. Use a machine shop that has done benz work before. Be sure to buy OEM valve guides with matching seals. Don't rely on somebody like NAPA or PepBoys to supply them. They won't be good enough.
There's a different thread asking about fuel delivery options for this motor.
Lastly and most important. Get the engine books. It's a 2 volume set and they're relatively cheap. If these guys don't sell them (this site does sell parts after all), visit ebay or call 1-800-for-merc (benz directly).