Doug,
There is glass polish available if the glass is not pitted from moisture being between the glass panes for an extended time. However, if the glass is pitted, you will need to replace the glass pane or put up with the spots.
If you clean the glass properly and replace the seal in a low humidity environment, there is no need to purge the air between the panes or inject an inert gas.
Even if you can find a window assembly that fits your coach at a reasonable price, you still have the problem of painting the window frame to match the rest of the windows because the window frames on your coach are painted to match the coach unlike the Patriots that have black window frames.
Gerald