Just my two-cents.
I prefer to drain the oil from the GRBX prior to removal,because I hate the mess the stuff makes when I pull the D/shaft out of the back of the tranny.
...and yes Factory service manuals are worth every penny-they can go for cheap on Ebay.

Like i said already. Get a manual and follow the steps as a guide. You can do it.

As Dodgy said,theres nothing wrong with"how to manuals"cause nobody is infallable.As well as buying one you might consider jacking it up and getting it on stands(nice and high)then calling a mobile mechanic and asking him if you can be his second man...cause you want to learn for future referance how to change a clutch.

$160.00 is only about 2 hours work which is reasonable if in doulbt,it's worth a try.

Get yourself a Gregories service & repair manual for a Datsun 1200 [try eBay] they are cheap & are writen for the home maintainer.
They have lots of photos showing how things are done & should be one of the first things you buy whenever you get another car. They will save you a lot more than their purchase price with the first screw-up that you DON'T make as a result of reading it twice & fixing it once.

For what it's worth, I've been a mechanic all my adult life & I have a book case full of Datsun manuals. Real mechanics DO read the manual when necessary despite what some backyarders might tell you.

Hmmm seems like too much for me. Id get it jacked up, engine supported, gear stik out and g box out, but thats all i could probably do.. I might need some help.. I thought id try it, everywhere i called today quoted $160+, all i needed was labour, ive already got the clutch. Didnt think it took that long.

Haha im pretty happy with the A series right now!! Conversion for later!

unless its my car and it all sits at least 20mm higher than its supposed to then just whip it all out and do an engine conversion just for the sake of a new tunnel

would be quicker ay piggy

Easy as mate The boxes weigh next to nothing which helps to. If you have a manual follow the instructions if not there is probably a manual on here somewhere.

minor detail pigdog lol, angle grinder takes care of that.
so ok before you undo any of the bolts under the car, undo the circlip that hold on the gearstick and remove the gearstick.
there will always be something i would forget to write down lol

have fun getting the gearbox out with the gearstick still attatched

Jack the car up.
Remove tail shaft marking the position on the coupling at the diff end.
Undoing the clutch cable and any wires that attached to the gear box.
Removing the bolts that join the gear box to the engine leaving 2 bolts on opp sides to hold it in place.
undo the gearbox mount.
then removing the 2 bolts left in the gearbox.
sliding the gearbox away from the motor.
then removing the preasure plate and clutch from the fly wheel.
Insepcting the fly wheel for warping or hot spots machine if necessary.
Inspect the oil seal for weaping replace if necessary.
checking the replacment clutch is the right one.
Replacing the clutch and the preasure plate and realligning with a sprocket tool to hold in place.
Tensioning the preasure plate bolts to specs in a x pattern.
replacing the throw bearing.
Re install the gearbox and clutch cable and then re install the tail shaft making sure to line up the marks on the tail shaft.
Adjust the clutch cable and your on your way.