Remove outer ring
I just did mine. You have to take a razor knife [purchase at a building supply] and slide the blade behind the outer trim ring and cut threw the caulk that holds it on. Lubricate the knife with liquid soap and it will cut threw fairly easy. The knife has to be long and flexible. I used one with the break away blades. [You may break a blade or two]. Then go in the cabin and remove the screws on the flange, then go outside and push on the window frame to remove. There is a possibility that someone may have caulked the inside as well, in that case you will have to try and cut the caul as on the outside. When you put the windows back in make sure you DO NOT culk the inside. If you have a leak in the future, culking the inside will only hide the leak and cause the water to get between the core. When I put the windows back together I didn't put the outside ring on, because the holes where cut so well that the caulk covered the gap nicely. You just have to be able to lay down a neat bead. It looks better too. It all depends on how god the holes where cut to fit the window. I used 3M 4200. Also this way you can keep an eye on the caulk insted of hideing it. Probably the hardest thing was to remove the old caulk from the ouside cabin wall after I removed the outer ring.