Most of my MB's were CPO cars, and I found that while the prices were slightly higher than private sales, the cars were truly the pick of the litter in the used market. Yes, I did have my indie tech give the cars a quick once-over, just to be sure, but he never found a flaw in any of them.
I'm not sure about today, but at one time MB financed any Mercedes used car on a dealers lot. Fall in love with a something like a 1969 280SL, but can't swing it all in cash? MB would finance it, and at a pretty good rate. I bought a creampuff 190E 2.3-16V and MB Canada's rate was far lower than the bank offered.