I have the FP Performance kit. I am very happy with it. You don't need to have Ford install it for the warranty. If you read the warranty document on the FP site it tells you any ASE certified tech can do it.
I did mine at my son's shop, he printed me a work order. I emailed it, the receipt for the kit and a picture of the rack with all his ASE techs certifications to FP, I had a confirmation back in less than two hours confirming my warranty.
You should not have to pay more than an hour labor for the install. Also, if you shop around you can get the kit for close to $500, mine was $509 from Levitton Ford.