If you're going to replace fanbelts etc then you may as well replace the tensioner bearing also.
If you're going to replace the timing belt then you may as well replace the water pump as it's cheaper in the long run with the labour costs and it's a part that if it fails, it can cause a lot of damage.
Check thermostat housing for corrosion and if there is corrosion on it then also check under the intake manifold for all the various cooling and heater hose aluminium connections/nipples (hmmmmm nipples ). If there's corrosion on some aluminium parts then there's a good chance that there will be others corroding away. Try and use original nissan coolant as it's not as corrosive as other coolants.
Reverse flush the whole cooling system: cleans out the heater core. Pressure test also.
Engine flush: Cleans out oil deposits and other gunk.
Brake fluid flush and replace: brake fluid is hydroscopic which means it absorbs water. Not good for brake systems. This is important especially if you live near water or in high humidity areas. You can also get your fluid tested at regular service intervals. Check brake lines and vaccuum hoses to brake booster. Actually check all vacuum lines and intake hoses from turbo to intake manifold.
Same goes for clutch fluid, and power steering. Check hoses for cracking and brittleness. Replace as necessary or if you want to be safe, replace them all anyway. Go on eBay and buy a whole silicon hose kit and put pretty blue or red hoses throughout the engine bay
Change oxgen sensor, water temp sensor and oil pressure sensor if you want to be really really sure, just like the irishman who puts on two condoms, to be shure, to be shure!
Check fuel lines, change fuel filter, check fuel pressure regulator (replace if you think like an irish gigolo).
Check battery acid level and age. There are testers for this. Decent workshops should have a multitude of testers some may even have a scan tool to plug into the ECU to test for any fault codes. Put it on your list of things for them to do. Check other electrical bits for fraying, wearing, discolouration of covers/wires etc etc.
Change oil in transmission, and diff. Flush it if you can. Check/change universal bearings, pivot bearings, wheel bearings. Check suspension and steering bearings, bushings, pivots, arms etc etc etc. Basically anything that moves, make sure it moves correctly, anything that isn't supposed to move, check to make sure it doesn't move.
If you're talking a _MAJOR_ service then thats what I'd be doing at least. Getting a workshop to do it may put the cost up over the $1K mark ( especially with replacing most things) but if you make a list and check a lot of the easier bits yourself then it's a lot cheaper. It's not as hard if you just go through it logically and use common sense. If you check things yourself, make a list and tell the workshop what you did and what you found. They won't take responsibility for anything that goes wrong if they didn't check it themselves.
There's plenty of sites and tutorials around online. They'll save you money and you'll feel good about doing it yourself. (maybe, this isn't guarenteed and some people just shouldn't touch mechanical things. If you are one of these people, work hard for money and pay someone who likes to touch mechanical things).
Hope that helps,
Hermit_