Cliff,
I have these seats, you won't need to build the seatbacks that come with the RV-10. Classic Aero's back seats are velcro and hinged in place, easy to flip up or remove. The cost will vary depending on leather, vinyl or cloth. I have the leather, top quality. They have prices on their site. If you plan to use them save some shipping costs to your home and have Van's deliver them to Classic for covering direct. Currently they only offer seats, a glareshield pinch weld and basic carpet for the RV-10 Luke has said that they plan a full interior like they have for the 6/7/8/9 but it hasn't materialized yet.
They do use a well know leather company, Perone I believe, so matching other interior panels is not an issue if they still don't offer the full interior when you are ready.
OH yeah...last heard Van's won't allow you to remove the Oregon Aero seats from your finish kit order...but...they are SUPER good seats.