Yes, the K&N just goes in place of your current air filter. They are more efficient than the paper ones. You can pick them up at any Advance Auto or Autozone.
As far as a dual exhaust, you really don't need to buy a rear bumper for yours. Most shops will bend the rear pipes to fit under your current bumper. I had my local shop cut off the pipes right after the cat converters and go 2 1/4" back from there. I did not add an h-pipe or anything, but I did use glass pack mufflers instead of flowmaster mufflers. It was a bit cheaper that way, and my Son bought it for me for my birthday present.

The tail pipes were actually from a 1995 Mustang GT that fit right over the rear end. They had the turn downs, and the bend towards the ground at the ends without tips. I'm not sure if you can see them in my photos or not, but I may add tips later on.