No airlock issues if you drain from the bottom of the radiator and refill carefully. To do a full flush you need to drain the fluid from the engine block too which will be difficult and you'll be more at risk of getting a lot of air in the system. I recommend only replacing what you drain from the radiator which was around 6L when I did it (there's approx 8.7L total coolant in system) There is a bleed screw at the top right of the engine bay near the firewall which you need to remove when you refill, coolant will bubble through it whilst you're filling it and when it overflows out with no bubbles replace the bleed screw and continue filling. You shouldn't get any air in the system that way, make sure you pour slowly.
Brake fluid is easy, best method is using two people. I bought one of those Gunson Eezebleed things you attach to the spare wheel to pressurise the system but unfortunately it doesn't fit the Z master cylinder. NEVER let the reservoir run dry or you will he a major air problems. See this thread for bleeding order http://www.350z-uk.com/topic/21148-bleeding-brakes/ be careful with the bleed nipples they are prone to rounding. I soaked mine in plus gas releasing spray the night before then cracked each nipple with a six point socket to avoid rounding with the flats on a spanner. I found it difficult to get a flare nut spanner to fit the nipples properly so just used a normal spanner carefully.
Diff and gearbox are easy, just make sure you remove the fill plug first, because if you drain all the fluid and find out the fill plug is seized then you will be stuck! As above Draper syringe works well. Need a 10mm hex for these.
Recommend you replace spark plugs too if they are due. Only use genuine fluids on diff/gearbox and coolant.