It sounds like you have had a rather unpleasant experience with your newly acquired MB. I agree with the others.... I would take it to your local MB dealer, or an independent MB repair specialist to see if they can diagnose the problem(s).

Hopefully you will get your car back in perfect working order soon. Don't give up on it. I know that these problem can make one feel glum about a car and want to sell it, but this sounds like a simple problem. I have had those types of automobiles in the past. However, some were not so simple. I bought a 92' Acura Legend sedan about a year ago and the car was misrepresented. I later found out that the valve seals were defective (bad). When I would idle for a minute or longer at a traffic signal, or drive-thru, when I would accelerate, blue smelly smoke would billow from the exhaust initially, then it would stop. I had heard that was normal on those cars and not a cause for concerns. Those cars were also well known for headgasket woes, so I sold it.

Good luck and keep us informed!