an n2o install is pretty easy, but can be time consuming depending on how much custom work you want to do. I have roughly 10 hours in my install, but I hid everything pretty good. Here are a few pics of my install for some ideas.
http://www.woodysoutdoorpower.com/th...ttle-front.jpg (my RCA cords are silver, that isn't an n2o line)
http://www.woodysoutdoorpower.com/th...le-outside.jpg
http://www.woodysoutdoorpower.com/th...ttle-trunk.jpg
http://www.woodysoutdoorpower.com/th...o-switches.jpg
I ended up putting my solenoids (n2o, fuel and purge) under my rain gutter. All the stainless lines are covered in wire loom for an OEM look. All my wiring/main feed line are in OEM looms. For the bottle mount I made a plywood deck for a solid mount.
All in all you could probably install a NX wet kit in 4 hours, but if you want a permanent install it might take a little longer to hide your wires. I would recommend installing everything at once, because you will have places to run wires already opened up.