check for leaks underneath by the gearbox, the slave cylinder maybe leaking, is the clutch working ok
the loss of fluid is usually down to either a leak or a blown seal allowing the fluid to move to where it shouldn't
do a tps reset (in the guides section - resets the accelerator pedal as its fly by wire ) and the zed is known to get gummed up on the throttle body butterfly, use some carb cleaner on it
also check the air intake pipes are tight, this would occur if air is getting in after the maf
if you can change a wheel then you can change pads, its that simple
brembo's ?
just pull the clips out then the pins and remove the pads, copper grease the rear of the new ones
non brembo
http://www.350z-tech.com/zwiki/Brake_Pad_Installation
Spend the money on some upgraded pads and do them yourself, very easy, approx 1hr to do all 4
redstuff £109 for front and rear off CS
or go for ds2500 ferodo's
the oem pads are standard ferodo, i changed to redstuff and have not been disappointed