I do not believe you can remove anything in the interior. Usually the leak is in the vertical duct that goes up right behind the rear cap. If the leak is low enough you might be able to reach up behind the cap. Or the bottom portion of the cap can be removed but with a little difficulty. If the leak is high sometimes the entire rear cap must be removed to get access to this vertical duct. Give Winnebago a call and ask them but if I understand your situation this is what Winnebago told me when I had a journey.
Howard,Connie,& Bella,
One spoiled schnauzer
2007 Newmar KSDP
4dr Jeep Wrangler