dude you can pull the box out yourself, its not that hard really, its just the first time you do it you
think its going to be hard..... best way is to have a mate handy to help hold the weight, but i have done it myself before with just a 3t trolley jack.
A thrust bearing is fark all, $70 is what nissan charged me for a genuine koyo one, or here is one one TM for half that
http://www.trademe.co.nz/motors/car-parts-accessories/nissan/clutches/auction-548695457.htm
The brand of clutch wont be too much of a issue as long as the bearing contacts the fingers or whatever they are called on the pressure plate and you have got a 99% chance they will, clutches for SR are clutches for SR's if you catch my drift.
I have a exedy hyper single, exedy recommend the stock bearing and other companies say for this clutch you need the Z32 bearing..... so there you go the different companies cant even agree, which means if its for a SR then just stick it in, it will fit.
Hours to do..... allow a afternoon going into the evening if its your first time.
If you need any guidance there are many people on here who can talk you through it
DONT get it done by a shop, as that will cost you heaps, and remember on here you are going to get advise from british people who by nature are pedantic as hell about stuff so dont panic