excedy clutch is best imo, looking around £250 for that if you want a slightly uprated one.
relativly straight forward job just hard to get at top gearbox bolts.
undo starter motor
unclip wiring and remove gear lever (need circlip pliers)
undo clutch slave cylinder
undo all the bell housing bolts attaching the gearbox to engine and the gearbox subframe bolts, and if your strong enough and the car isnt too high off the ground wiggle the box out and rest on your chest then ease it down and slide out the way
then just unbolt the pressure plate and off comes the clutch.
keep a full day free if its the first time you have done one and best to get a copy of the nissan service manual for torque settings etc.
also, a clutch alignment tool is very handy and cheap enough.
not sure what would be next best thing, maybe a blue print one if they make them as a stock replacement.
a quick search on ebay usually brings up quite a few excedy clutches. got mine off Japan Import Car ltd Skyline Parts Specialist/Breakers although davew (gtr shop)may have something knocking around.
failing that try import car parts in durham, theyre quite good for the stock replacement parts that are hard to find.