The common school of thought is that sealed dual pane windows cannot be repaired, they need to be replaced.
However, this is not true. I had a couple fog up on my '07 Bus and my dealer, http://www.kingscampers.com
took them out, gave them to a local vendor who takes them apart, repairs the seal, vacuums them out, and refills with inert gas. They work great and hold up well after that. Kings works on any brand coach but they're up in Wisconsin, which is probably not nearby for most of you.
However, if they can do it, I'm sure there are others who can repair your windows nearby you rather than having to replace window panes.