The feedback here is very helpful.

Junkman...you have successfully scared that @#(@* out of me. Time for a gut check; do I have a stomach for this?

My motivation is:
1) I work with computers all day. I'm a computer guy.
2) I HATE computers. I really hate computers in cars and ovens.
3) I love diesels.
4) Love the character of the 300D
5) I've enjoyed tinkering with my '81 Rabbit pickup diesel. This has been cheap fun.
6) I might even be able to do some of the maintenance to the old 300D myself.

So, the newer models with their complexity/computers/sensors makes me think -- heck, if yer gonna do that then just go out and buy a boring Japanese gas car - which kinda defeats the purpose.

I suspect I'm not the only one of you who face this conundrum. At this point, I guess you guys have me thinking this might be a money-pit decision point for me.

Thanks for the food for thought. This web site / forum has been REALLY helpful the last month or so as I feel in love with these old Mercedes.