The full pad is a bit tricky to install. You don't have to do anything under the dash, but you do have to remove the trim right under the windshield. It is all easier to do when the whole windshield is out, but with a small screwdriver and, in some spots a bent one, it can be done. Let's put it this way: I did it. For the rest, you need to do a bit of scraping and, possibly, sanding to get the upper dash surface cleaned up, and from there on it's two coats of contact glue and a bit of patience. No rocket science.
Bob S.