Please hire a good roof contractor who has handled Metal Roof's before. There are so many factors. Will your trusses support this? They need to do the math. They need to know how many layers of shingles and what type of roof sheeting (for weight) is up there. There are also special screws with rubber grommets many metal roofs use. A contractor will have the bender and chopper to extrude the cap and valley pieces. You need much of this information before you get the permit. Good luck to your installation. Metal rooves are fabulous and a great investment.