I've had my W210 for over 2 years now and I've gotten by without any special diagnostic tools or specific manuals. Working on the engine is very similar to working on the older OM60x engines like the '87 300D that I used to have. I've read here that you can minimize the chance of breaking the glow plugs by removing them with the engine warm. Fuel leaks are common, but it's just rubber and it's a DIY job if you're at least somewhat mechanically inclined. Just don't expect the fuel system to be as bullet-proof as it is on the OM61x engines. There's a lot more rubber and plastic on the new one. But once you replace the affected parts you won't have to worry about it again for at least another few years. Lower control arm bushings tend to wear out and that typically shows up as a steering wheel shake around 55 mph. I would be most concerned about the front spring perches which tend to rust away and break off and the rust is not always apparent from the outside. Sometimes you have to temporarily peel off the undercoating to take a peek. Overall, the newer diesels are much more refined and luxurious than the older ones. They're just more sensitive and vulnerable in certain areas.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL