So we have a window leak in our 3901wb. The bedroom window on passenger side is leaking. I noticed some water on the cabinet. So how do you reseal these windows ? Do you remove the window and silicone around and re install ?

There's a good place to use silicone somewhere, but in my opinion nowhere on a rv.
Remove the window, clean all surfaces & use butyl tape which can be purchased at Ace Hardware or most any rv shop.