Not that easy to slide in new upright for window. I would wait till you can tell where your framing is. Sometimes in the morning and sun just right I can see every frame member. If a window frame doesn't have proper support your asking for problems, short term and long term. Also it's not hard to find an RV around Seattle with the skin falling off and take a peak of where framing is. Maybe you can offer new roll of duct tape and a 6 pack? You also might be able to pull the window and you can sneak a peak looking down in-between the inside of the skin and bottom of window frame. I've had good results using "arctic" white to match my colors (Ace hardware)