I think another person said this but it is a single piece. The side facing in has about 9-12 screws counter sunk around the border/frame that have to be removed. Once those are out, pry up the border gently. It will not want to because the metal door is filled with expansion foam. It may take some finagling. Once removed, That is what holds the grid in place. It should more or less come right out. Then you can tint it. Install is reverse of removal, and seal with a bead of silicone/caulk on the inside of the removed piece

It’s double-paned, argon filled and has a n aluminum frame sandwiched around the perimeter of it filled with silica beads.