Welcome to the MB experience!
There are a lot of posts here about the difference in quality between MBs and other makes, and opinions go both ways but seem predominately to come down in favor of MB, all things considered.
Your car, like mine, is in its adolescence, just over 100k miles. There are things that go lame on you at this time of life, sort of like growing pains in humans. Engine mounts, water pumps, sway bar bushings, and the list goes on, but the W124 cars have great "bones" and the basic engine and transmission will give you lots of happy miles if it was well maintained before you got it (and you will certainly do a great job of maintaining it, since you are taking the time and trouble to come to this site to learn more about 'em).
The other thing that I've noticed with mine is that repairs seem to come in groups. You'll go 15-20k miles without a hitch then 3 things will go lame, and you'll wonder "What next?" but if you tough it out, usually things will smooth out again for a good long while.