Rear shock 10 bar. That's about 145psi. Please be very aware that a gas under pressure can kill you!
Having said that, the first time I rebuilt a so-called non-rebuilable rear shock I was all togged up with leather apron, face shield etc etc and got a very disappointing pop when I drilled through the end cap to release the gas. High pressure but relatively small volume.
When rebuilding you must make absolutely sure that there's no air bubbles. When I'm pumping the damper rod through the fluid I give it a few sharp cracks with a brass mallet to 'shock' the air bubbles out of the damper valve.
You will spill oil all over the floor. Not just once. Then you'll pull the damper rod up too high, suck air in and have to start again. Be prepared to overflow the oil just to make sure there's no air pockets hiding.
The nitrogen is contained in a rubber bladder in the reservoir tank. I like to fit this all deflated so that there's essentially too much oil in the shock. Then I set one of the banjo bolts on the hole at a high point and let any remaining air bubbles settle at this high point. Tapping the shock body helps release any sneaky bubbles that are hiding.
Oh yeah, forgot to say that you'll need to fit a valve to the reservoir tank cap so that you can refill the gas. There's a couple of types generally used. Either a schrader valve, which is the same as the one you see on your tyres, or a rubber bung type. The latter requires a hypodermic needle to refill, whereas the schrader can use a normal airline fitting that you can buy anywhere.