Help Installing a train horn (air horn)

[dapaintballer331]

So far I've purchased nearly everything but the horns themselves. I have a compressor, air tank, hoses, fittings, even a solenoid valve. I've never modded a car before, but have done a lot of solenoid & air work before with computer controlled air cannons, computer controlled paintball guns, and more.

If you can answer any of my questions that would be great, I'm definitely a newbie to car parts (but not electronics).

My only issues so far are:
a) Getting an air hose from the trunk to the undercarriage
b) Wiring the stock horn to the solenoid valve

Questions:
1) Do I need to drill holes somewhere in the trunk? Are certain places better than others? (I know minivans sometimes already have a path, where a spare tire goes)
2) Is there an easy way to remove the "grill" to my nitro, to install the horns in front of the radiator?
3) Where is the "ignition power source" which supplies 12v when the nirto is running?
4) Is there an easy location / way to identify wires involving the horn switch, so I can setup a relay to my solenoid & it's power?

Thanks a lot for your help