Having ford install would be a terrible idea. They will charge you can arm and a leg and could possibly void your warranty. When it comes to what will and will not void your warranty it depends on the dealer. There is a law that states your warranty can't be voided unless the aftermarket part caused the issue. It would be smart to call your dealer and ask how they feel about bolt-on parts like intake and exhaust.
You should see an increase in gas mileage. You are opening things up, not restricting them.