1. I am not a Bigfoot
2. It's difficult to see much in the photos
I don't think you have much to worry about.
From what I can see... the little bit of staining around the window could be from something as simple as interior condensation or a window being left open in the rain. It doesn't look like a major long-term problem.
As for the exterior caulk work... well at least someone attempted some preventative maintenance... they just didn't do a very good job. I think you will find that since silicone doesn't adhere very well to fiberglass gel-coat, you can simply rub your finger on it to remove most of it. You can then use Goo Be Gone, Mineral Spirits, Varsol, etc., to remove any remaining residue.
The best solution for water intrusion would be to completely remove the body item (the belly-band for example) and any old sealant. Clean the area and re-seal/install. If you are not up to that then you can get a really nice new silicone job (even for a novice) by using simple "painters tape" to "mask" around the area to be sealed. Put the tape just slightly above/beside the joint to be filled. Then tape the item (top edge of the bell band) very close to the joint. Now you can run a bead of silicone into the joint (don't go overboard, a little goes a long way). Use your finger or a tool to smooth out the sealant and to force it into the gap. Now, while the silicone is still "wet" you can peel off the tape and you will have a professional looking job.
PS. Have a fantastic trip picking up the new trailer. My family once lived in Victoria, on Vancouver Island, and my girlfriend grew up in and around Vancouver. You sure will be passing thru and visiting some beautiful areas.