It is a time consuming job, I hope you have a big work shop. Start by removing all the doors, windows, lights and exterior trim, you will be kept busy getting all the sealer off. You then need to remove the staples from the front, rear, and top where the panels overlap.
Start at the bottom, dig out the caulking in the lap seam, remove the staples and pull the sheet down, this will likely require two pairs of hands. Once opened up look for signs of water penetration and rot and determine the source, this may be the cause of the delamination.
Handle the new panels carefully, don't damage the lip that goes into the lap seam or you will have a real battle. An insulation stapler is not adequate, rent a compressor and air stapler. Make sure you thoroughly caulk and seal with products designed for rv use, don't skimp here or you will pay later. Of course if the walls are laminated all this is moot.