I just did a head job/valve job myself on my 300e!
One of the reasons I did it was because I already decided to keep driving this vehicle a little bit longer and NOT to buy a newer Mercedes.
My 300e is relatively easy to work on to the point that I, as a DIY'er, can do a lot of the repairs needed myself. When I first got the vehicle, I took it to the stealership for repairs once or twice. They were BAD experiences. They were the last time they touched my car. Let's just say, they treat you different when you have an older MB...
On the other hand, I would not dream to do any major work on the new very complex MB's (or any new vehicle) that are in the market now.
When I get a new(er) vehicle, safety and reliability are major concerns.
Well, safety has improved on all vehicles, some even better than MB's, and based on current reliability and my experience with my local Stealership, my next vehicle will not be a MB.
My wife wants a ML but, with all the problems people had with these vehicles...NO way! Sadly, I am trying to talk her into a different brand of vehicle.