Metra Dash Kit 95-7417 is your solution. There are no true DD kits for that car. You will have to do some work yourself to make it work. It is not hard, just some plastic trimming.
As far as harnesses it depends on whether or not you have the Bose system or not. Google is your friend.
2009 Ford Flex Limited with Sync.
"Will I respect the winner in the battle for my mind?" - Cy Curnin
USE YOUR ASHTRAY NOT YOUR WINDOW! DONT BE A LAZY SLOB LITTERBUG!