you have to be prepared to spend money on it for the "privilege" to drive it. A transmission from the MB dealership will be around $ 2,500, air conditioning repairs are expensive, I paid $2,500 for a ringgear. If you can do things yourself, then it looks a lot better, provided you have the time and facilities. You can see on this forum how brake rotors are replaced (my next project) and a lot more, but if you have to pay for it, it is an expensive car.
With that milage, you better have it checked completely including a compression test. I saw at least 20 different 420s over a 3 months period before I settled on mine, which, incidentally, was the first I saw at a dealer and was still available 3 months later.
But I second Bruce's thought, it is a hobby for me, too and I have another car just in case.
Welcome to the disease...