Thanks for the list jdd

The transfer case gear is a cheap and easy fix. Don't fret it at all.

Do we need to worry about the DPF and EGR on the e53 3.0d engine?
Does the sump oil pick-up need to be checked for gunk build up?

I had my EGR out a few months ago - just an inspection. Appeared relatively clean so back in it went. While some people believe EGR is the root of all evil, I am of the opinion that the engine is designed to run with the cooling effect of the EGR to reduce combustion chamber temps. So I'll leave it in place and like everything else - just maintain the system.

Depending on the year of manufacture, you may or may not have a DPF fitted.
Mine is a June 2004 build and it doesn't have one (thankfully). I'm not sure exactly when these were fitted to the vehicles sold in Oz.

EGR is probably worth checking/cleaning every 50,000km or so.
I cleaned mine soon after I first bought the vehicle at around 150,000km and it was badly chocked, although it probably depends on how the vehicle is driven as to how often this needs cleaning.

As far as the oil pickup is concerned, I'm not aware this can be checked/cleaned without pulling the sump off and this appears to require major work. My advice here is to ensure regular oil changes with the correct grade of approved oil.

Mine is an 11/05 build and gas no DPF. My understanding is that all Australian spec diesel E53's did not have one fitted. Some have catalytic converters however.