It's a lot of work but if you've got all the interior out already its not too bad. Remove the front/rear seats, rear seat back rest, the A and C pillar panels, the visors w/ snap hooks, dome light, upper console, the coat hooks, it held in by a few tabs if i remember correctly. carefully pull it down and it comes out. Best to have a second person helping you.
Once you take it off you'll notice theres pretty much nothing up there just a thin sheet metal on the roof and some support braces.
Second skin is suppose to be good but for the money you can't beat Raammat i think your mostly paying for the name and a slightly thicker amount of butyl. It's like Dynamat Xtreme (i have some dynamat xtreme in mine) it's a little thicker and a lot harder to work with.