I would not bother with the foil bubble kit sold by Camping World and others.
Bonded Logic Heat/Sound Insulation - JCWhitney
This what we used on our former Minnie Winnie. You do have to pull the seats and carpet which has not insulation under it. Cut the edges of the insulation about 1: short of the door and engine cover edges. Use the high temp spray adhesive from Whitney to glue the insulation (foil side out) to the engine cover and seal the edges with the aluminum tape.
It took me about 5 hours all total to do mine. It made a 1000% improvement. I do not understand why the manufacturers do not do this in the first place. In the south, the floor and engine cover really get HOT...especially the passenger side.