Hunter interior "quilting" is somewhat like kevlar in strength and is well worth trying to keep. Try reading up on general mildew removal on Google as well as trying suggestions found here. I "think" that there is a "Bomb" that is also effective in killing mold spores than may have crept in behind the stitching.
In as much as mildew does not like sunlight or fresh air, it might be worth the effort to remove the top and leave it open to air for at least a week (weather permitting of course)
As the most common place water gets into the walls is at the windows
, it might be a good idea to pull them out for recaulking and leave then out for a while as well to assure a good drying out behind the wall covering.
BTW: DO NOT attempt to just reseal the windows
by adding more silicone stuff, it doesn't work and will lead to more leaks
& damage in the future. You have to take them out, clean the old putty off and install with new RV putty tape.
And, as it does rain on occasion up your way, as Donna mentioned, keeping a pan of drying agent inside is always a good idea.