This is the first hatch I've seen that has separated. The door skins are glued in place with a GM Structural Epoxy adhesive P/N 12345726. The hatch may also use this type of construction, but I'm not sure how well you could prep the panels for re-gluing without first separating the two panels. I've attached a pdf showing how the service manual describes replacing a door skin. I would check with a local body shop to see how they would recommend repairing the hatch.