Service/repair Manuals & Oils

15w40 mineral oil will be fine.
If you look for an SL grade as this is the latest unless you have plenty of money to spend on the synthetic stuff. Its good but its expensive.
Either of the books mentioned are OK.

Gday Mouldy
I agree stay with the mineral oil or semi synthetic.

Look out for fully synthetic oil. As i have been told by a Mechanical Engineer that unless you engine is designed for the stuff it can do more harm than good.

My advice would be to get a Nissan manual. They are more expensive but they have alot more information in them. I have both the Nissan and Gregory's and I noticed some differences with clearences, settings etc. Not vastly different, but still different. For general work though, the Gregory's is good. As for your oil, go with mineral. Sythetic is designed to last longer so you can spread the serviceing intervals out. That's all good and well when it comes to a petrol engine but it doesn't work with a diesel. You will still have to do your oil changes at 5000 kms regardless of what oil you use and you will be wasting money by using synthetic. By all means use it in you transfer, gearbox and front diff and you can spread out your oil change intervals and save money. Don't use it in your rear diff if you have a limited slip, as you have to change the oil too frequently for synthetic to be cost effective. This advise came straight out of the mobil reps mouth about 8 months ago when I asked him the same question. I ended up using penrite 15w 40 as it has a high detergent ratio to keep the soot in suspension so the filters can remove it. I hope this helps you.

You need to change the oil in the gearbox, transfer and difffs every 40000 kms or 24 mths. The gearbox and transfer take 75W 90 GL4 grade oil. The gearbox needs around 4 ltrs and the transfer needs around 2.5 ltrs. The front diff takes around 2.5 ltrs of 80W 90 GL5 and the rear takes around 2.5 ltrs of LS 140 GL5. If you are going to takle any of these, do yourself a favour and buy a small drum pump. It makes life a lot easier when you put the oil back in.