I don't think you will see much increase in performance or mileage by installing just an aftermarket Cold Air Intake. These seem to help when installed with an aftermarket exhaust system. The two need each other to work well. The aftermarket CAI will increase enging noise quite a bit when accelerating hard. It won't be louder at idle or at a steady speed. My experience with the Airaid TBS has been a increase in off idle acceleration, but no gain in mileage.
As you may have seen from some of my posts, I have the Volant CAI, the Airaid TBS and the Gibson single cat back system installed on my Armada. This combination has worked well for me, with significant increases in performance, but very little in mileage increase. But the increase in performance hasn't cost me any mileage, which is a good thing.
I like the Volant because it is a true CAI. It is completely sealed to the engine compartment hot air, taking all it's air from the fenderwell. Most other aftermarket CAI units are not sealed, and take in some hot air from the engine compartment.
You don't have to have the TBS to install the other devices, but I have proven to myself with back to back test runs that it does increase my acceleration performance.
The three items discussed above are easy to install. Any owner can install them with basic hand tools and some guidance from this forum.