nitrous is perfectly safe on a stock motor provided you are smart about it..
dry kit= the nitrous kit injects only the nitrous, the cars fuel system has to compensate for the fuel
wet kit= the nitrous kit injects nitrous and fuel at the same time.
i would NOT under any circumstances go with a dry kit. while they do work fine, it pushes your injectors alot closer to their maximum output.. as well, for myself i dont like the fact that the car has to "compensate" for the nitrous being sprayed in, while the kits are designed this way, common sence would show that there would be a very small lean condition every time you hit the juice, until the injectors catch up..
and nitrous + lean =
... so to give myself peace of mind, i have a wet kit.
with that said, regardless of wich kit you use there are certian saftey features that you definately should get.
saftey gear: WOT(wide open throttle) switch.. makes it so that your nitrous is only active during wide open throttle
colder plugs (hotter burning plugs, like plattinum's are BAD with nitrous, 2 heat ranges colder than stock are usually perfect
window switch = makes it so the nitrous only sprays between set rpm (3000-5800 is perfect IMO) this stops the chance of a backfire, or of fuel puddling in the intake, wich would mean kaboom.
blowdown tube: if the bottle pressure reaches and unsafe level, it vents the nitrous, saving a kaboom.
not needed, but reccomended:
purge, keeps air out of the line, so you get a "full" hit if spray every time
bottle heater: keep the pressure at 1000 psi where it is optimal