Al, the cooled seats have a soft plastic duct molded in them that goes through the foam. I can only speak for the 3rd Generation trucks, in which I've changed several seat covers. I've always removed the seat. It's not hard and offers access to remove any side trim. Watch the video on The Seat Shop website. It's a great video showing all the steps. Then you can decide if you want to try it without removing the seat.
By removing it and bringing it into the shop/dining room/bedroom you can roll around on the floor with it and work much more easily.
If their's no video for the 4th Gen, look at the one for an F-150 or a 3rd Gen Expedition and you'll get pretty much the same thing.
