First, will I need to get a tune to accomodate the kit?
If its a wet kit and 125shot or less i wouldn't bother tuning it. They jet their kits so rich that its not needed. Plus our factory tunes are so bland from the factory you dont need to. If you can afford it i would as they will be able to get more power from the car.
Also, is it possible to set up a bottle pressure gauge inside the car?
They sell gauges that go in gauge pods on the Apiller etc.. so you can read the pressure right there in the car.
And can I turn on the bottle from inside the car or does that need to be done manually before I spray?
Depends how and where you mount the bottle and if you get a remote bottle opener or not. I have my bottle mounted in front of the MACH1000 stereo right behind the back seats so i can reach back and open it by hand while driving. Or you can get a bottle opener which cost a ton, and use that route.
How hard is the install?
Depends how good you are at installing things. Overall its easy. You mount a bottle with some bolts, run some lines from the bottle to the front, mount the solenoids and install the fitting to get fuel on the fuel rail,then its just wiring it up. Its not bad at all but it will take the average person 4-6 hours i would say.
My setup for the bottle:
