Sticky side down tends to work the best in my experience. That means the shiny side is up.

Not really sure about how much it helps with engine heat. I haven't really had an issue with the AC or windows not being able to offset whatever engine heat might be coming in so I never noticed.

As for the door panels, the only thing that snaps in are the switch panels. Otherwise you remove two screws and lift the door panel off the door. It just sits on their with several hooks. Nothing to snap off from prying the wrong way.

The pillar covers are another matter, but then it's usually only the rear one that gives you fits (at least on a crew cab)

 

Thanks, I have begun my Google searching and finding out much about resonance and vibrations CCL MLV etc. It is getting very technical. Just want to make sure I use the right product and do it right the first time. This site appears to be knowledgeable in the whole area don@sounddeadenershowdown.com .
Our cab gets a bit warm and need to run the AC constantly. Thinking maybe aheat shield to cover the huge exhaust under the passenger side might help...