Thanks for the warm welcome!!
Sadly, I've felt the first symptoms of "aluminitis". I've heard there's no real cure for it, so you're better off just letting it run its course.
Wow, lots of good information. It looks like what I thought would be a 2 day project to replace the subfloor will be a bit more involved than I had originally thought. I'm looking forward to doing this right though, and understanding how these things are rebuilt, so there's no time like the present to get started.
From what it sounds like, it's best to remove the underbelly so I can get at the old insulation, the bolts to the subfloor, and have easy access to c-channel that houses the floor. After that, a little POR15 and apoxy sealant before buttoning her back up.
I must admit that taking off the underbelly is a bit of a daunting task for a newbie... I suppose I'll read up on how to remove and replace rivets.
Here are a couple of pics of the Airstream...