Where are you located? I've been kind of on the fence during the last several months as to whether I should sell my '96 E300D. I put in on Ebay a couple times but didn't get what I wanted for it. If the price is right I would be willing to part with it. I'm only trying to limit my loss to a few thousand dollars.
If you're not crazy about the extra power of the turbodiesels, I would say go with a non-turbo OM606 as those are more reliable in the long term, especially the ones with the older-style transmission (95-96). There's fewer electronics and parts to break on them. The fuel economy is about the same from what I've heard, at least among the W210 models (96 and later). The W124 probably gets an extra 2 mpg or so because it's lighter. With the W210 cars be very careful about the front spring perches. If they're rusted and one of them snaps you could lose control of the vehicle.
I had to have mine replaced as soon as I got the car.
If by any chance you're interested in my car (it's in great shape overall) PM me and we can go from there.