There are several threads about removing the inner pane of Vista View windows, and it isn't too difficult. Simply scribe lines in the inner plastic pane, crack the plastic, and carefully remove it from the window. Scrape the coating off the glass, and you're done. You can find some grey vinyl trim from places like CR Laurence to fill back in where the plastic was.
The double pane glass windows like those found in the Excellas is a little more tricky. You can remove the window from the trailer, lay it on a workbench or table, and carefully break out the inner pane. Clean the old glass, scrape the film off, trim it back out, and re-install the window. While the window is out would be a very good time to replace the gasket around it.