I have re-caulked the bathroom in a number of Airstreams. The GE Ivory silicone is the right color and is what is there now. Clean out as much of the old as possible before you apply the new. Cut the tip small, so you lay a narrow bead. Since it is inside and will be protected from the elements and is on fiberglass or ABS it will hold fine. You will be amazed at how much better it looks once you get it done.
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato