Ok, take a deep breath(outside the trailer) I took about a month of working on it in the evenings. I had bought the trailer the year before and used it for a year before gutting it. I looked at various wall choices from paneling to the tongue and groove pine that I ended up with.
First you should get it safe for you and your family. Do the floor first and any other water damage. Save the pieces you remove and use them as templates to cut new pieces. If the paneling is in good shape, then a good coat of paint
will make a big difference. The cabinetry does come out pretty easy when you look at it. Usually just a few screws.
As for the leak at the door, i would first look at the aluminum door frame at the bottom and see if the welds are cracked. This will allow the water to run into the trailer. If the frame welds are broken, clean them up really well and seal them ( I think I used some epoxy glue. Now when you put the floor back in, find some wood to go under the door frame to wedge the frame back into place and support it. Most people step on the frame going in and out causing it to break.
Next , go inside and close the door, see how much gap between the door and the lip of the frame. Go to a hardware store and get some stick on weather stripping about the size of the gap and install it on the lip all the way around (clean first).
Check the door and window, as the windows
leaked and caused the doors to rot from the inside. Use caulking to seal the edges and the window frame and if its as bad as mine, I would seal shut the whole window.
Here is a picture of mine after painting
the interior BEFORE gutting it.Fiberglass RV - Dudley's Album: Ventura - Picture
so you don't have to do it all at once