leak over cab Window?????

I would find a dealer that could perform a "leak" test, that was the only way that I found my LEAKS after "guessing" for over a year..My dealer charged $100.00 and allowed me to observe the test..

I would have the rig pressure tested ... finding leaks is a major PIA and the source is often a long way from where you think it is. If your sure the window is the actual source then removing the window and replacing the putty tape isn't very hard - lots of videos on Youtube.

Something else to consider. I ordered my 'C' new at a local dealer. When it came in, they invited me in for orientation. One of the things they showed me was the marker lights in the cabover. They removed the chrome covers to show me that there were no cracks in the underlying fiberglass. The covers are installed at the factory with high speed screwdrivers. If they over tighten, it can crack the fiberglass, creating a potential water leak that you'd never look there for. Mine was fine.