I'm new here so someone else might have to chime in.
This thread may help:
[Official] "Which intake should I buy for my Z?" thread.
There is also this site that has videos of exhausts, and increase numbers etc:
370Z Exhaust.com - Sound clips, photos + places to buy
As for where to buy, the vendors on the site seem to have great deals (especially during random sales events). I would check with them about pricing.
As for the tune, it seems like common practice to get the UpRev tuning software for the car.