My question involves a child custody case from the State of: Arizona

I was divorced in NY 10 years ago and am the custodial parent. I now reside in AZ and my ex-husband lives in Florida. My boys are now 16 and 18 years old.

My 16 yr old son would like to go and live with his dad in Florida and I agree that it would be good for him. Do I need to make my ex-husband the custodial parent. Obvisouly, I would no longer require child support seeing he would be living with his father. What legal steps do I need to take, if any?