I think the "you can't work on a modern car" thing is vastly overstated.
I can remember people saying that about my 1980 BMW 320i, with CIS injection. It was impossible to work on because it didn't have carbs.
People said the same thing about Motronics when it first came out, "the computer controls everything, you can't work on it."
Of course, shadetrees work on those (now) primitive cars all the time.
My view is this: An internal combustion engine is an internal combustion engine. The only thing that has changed, and not even that much, is the injection system. Sure, a lot of the injection parameters are increasingly controlled by computers, but its all the same basic principles. The reality is that the basics really have not changed.
Now, it often takes a while for scanners, code readers, good manuals, etc. to trickle down to the shadetrees, but it eventually happens. So, is it possible for the average guy to do a lot of work on a 2000 MB? Probably not. Will it be possible 6 years from now? I think so.
I've looked over my '01 C240 pretty closely, and have reviewed as much tech stuff as possible. It does have gadgets, but it generally doesn't seem that complex. I plan on keeping it 15 years, and plan on doing all of the maintance and repair work on it once the warranty/service runs out. If I have to buy special tools or code readers, I'll do it.
(that is just my opinion, admittedly based on past BMW ownership, not MB ownership. I think maybe more "DIY" stuff is made for BMWs, for some reason).