The routine work is owner work if you are competent: oil and filter changes, primary fuel filter and water separator servicing, impeller inspection, coolant checks, belt and hose inspection, anodes, and keeping records.
The high-pressure circuit is not, under any circumstances. Common-rail systems hold fuel at pressures capable of injecting through skin and causing life-threatening injury, and pressure can remain after shutdown. Never loosen a high-pressure line, never crack an injector to bleed a common-rail engine the way you would an older mechanical one, and never work on the rail, the high-pressure pump or the injectors.
Electronic diagnosis is the other boundary. Fault codes on these engines need the maker's tooling to read properly, and the code names a symptom rather than a cause. An owner can gather excellent evidence — conditions, readings, what changed, what the alarm said — and that evidence makes the technician's visit shorter and cheaper.
Bleeding after filter changes also differs from older engines: many common-rail systems self-prime or have a specified procedure. Follow the manual's procedure exactly.