Hey mate,
Not sure if you've already started doing the service but I did my 100k service about 2 weeks ago so while it's fresh in my mind I thought I would make a list for ya.....
1. Replaced water pump with new factory item (Done by tuner)
2. Replaced timing belt (Done by tuner - don't attempt this if you're unsure. I've had a fair bit of experience and I left it to the pros, just personal preference)
3. Replaced idler and tensioner bearings (Done by tuner)
4. Replaced oil filter (Done myself)
5. Replaced coolant (Done myself)
6. Replaced all the belts (alternator, power steering and AC) (Done by tuner as I CBF'd lol, but it's not to bad)
7. Drained and filled both front and back diffs (Done myself, this was very easy but you have to be careful when lying under the car, make sure you have the proper equipment)
8. Drained and filled the gearbox (Done myself) with RedLine shockproof (very expensive but the beez neez) - again just make sure you have the proper equipment to hoist the car
9. Cleaned and flow tested injectors (You'll have to get it done professionally, cost me $100, very good investment for an R32)
10. Replaced Air filter (I just put in a good quality K&N panel filter, good for a million Km's, just have to blow the dust out every now and then). If you're running pods, just give them a clean/ replace
11. Clean out your air flow meters, ensure you use good quality electric contact cleaner (you can pick up a can from Dick smith)
12. Changed spark plugs (Done myself). This is really easy mate, just make sure you have the right tools and pick up some anti-seize paste from an auto supplier (you put it on the thread of the sparkies so they don't get stuck in there when the engine gets hot)
and if you want to get technical....
13. Check your O2 sensors (on the dump pipes), mine personally had to be replaced, I wouldn't bother though if the car is running okay
If you take ya car to a reputable tuner when they do the more technical stuff, they will be able to tell if there is anything else that needs attention such as brake pads or tire tread condition.
Hope you've been saving ya pennies, a GTR service will be around $1k ,
Cheers,
Sean