Floor repair: Under internal slide lip

Have a '94 Dreamer by Alpenlite that took a hit from a tree this winter, which jarred a seal near the flooring and took in water before it could be detected. The affected floor around the leak has been prepped for repair, but I am unsure what my best option for getting at the floor below the inside lip of my slide without taking the entire thing out would be. The entire underbelly is enclosed with metal sheeting, which has deterred me from approaching the fix from the top down through the slide floor.

Thoughts?