I did the same as Adam for the 300se I currently have now. Having said that, its really a satisfaction as the car runs as smooth as new and *hardly* requires any other repairs or services ... said with fingers crossed.
The most expensive and worth-while thing I did for the 300se was a complete overhaul and change of springs/suspension ... the whole lot for RM7,000 (USD3,000).
If the value of passion and love for the MB exceeds the cost of repairs, might be worth the while to keep it.
However, if your gut feeling tells you otherwise, you're left with extra choices.
I think everyone else has said pretty much what has to be said, especially Bill.
Whatever you decide, we're always here to offer our support and humour. There wont be lack of either.