Here's what I've found out from Nissan UK: Early 2000 3.0 TDdi engines were prone to problems due to insufficient lubrication / oil capacity. All 3.0 TDdi's sold in the UK up to October 2000 were subject to a recall (fault code P1110) and the engines were replaced. I have checked with Nissan and the main dealer that serviced my Patrol and my engine has been replaced.
Hope this helps. If anyone has an early 2000 TDdi then I suggest you contact Nissan and ask them where you stand.
Here's a quick way for you to check whether you have the dodgy
engine: The oil capacity of the newer (improved ) engine is
different to the troublesome one. The oil capacity in your Owners
Manual will give you the information you need. The problem engine had an oil capacity of 5.7 Litres with oil filter (5.2 litres
without filter). The newer (improved engine) has a capacity of 8.2
litres (7.7 without filter) Check in your manual - mine has a
sticker with the new capacities (done when they replaced the engine). If you have the lower oil capacity you have the engine which was recalled and replaced in the UK.