Brenspeed will take care of your tunng needs. If i remember correctly, anything less than 125 shot is free with the purchase of the kit. dont quote me on that though.
Nitrous is not that hard really. I had a nitrous express kit on my mitsu 3000gt. I did the whole install myself in about 9 hours(wiring; fuel splice for the wet shot; fuel, nitrous and purge solenoid mounting;interior mounting for switches, bottle, brackets, blow thru pipe, and bottle heater) . if i did it again it would take 5. From what i hear the Zex kits are more straightforward and easier to install than most other kits.
A 75 shot is what i ran on the 3kgt. it was the max i dared on a 6 cylinder with stock internals. you should be safe up to 125 shot with a good tune. i would reccomend not going more than that. plus, its more than plenty. use higher than 93 octane as well just to be safe. I ran 104 sunoco in my 3kgt to prevent any possibilty of f-ing something up. yes, it can be overkill with 104 gas, but better safe than sorry.
The zex kits come with a WOT (Wide Open Throttle) switch that will activate the solenoids once the system is turned on. My system also worked this way. It is best this way so that you will be in high rpms at WOT. never spray under 1/2 the engines rev limiter (3000) and you should be just fine.
Two things that are "necessary" are a bottle heater and a nitrous pressure gauge. Your system will run like crap at 1/2 tank without them because it will not run at 1000psi like it should. trust me, ive been there. it made a difference of .3 seconds of et and 4 mph by the end of the night not having them, and I'm sure it will make the car run super rich.
On the nstall, like said before, take your time and do it right. find i cool place for the switch. I suggest the cigarette lighter in the center of the dash. nice convenient spot.
Good luck and happy spraying!!