It's hard to do without knowing what's above that window. In theory you can just cut the hole bigger and slip a new piece of framing into where you made the opening wider and just install a larger window. Wood framing like I had on the Lance wasn't bad, but if the frame is aluminum tube it's a whole lot more difficult.
The challenge is that there may be blocking for frame strength above the window, or 12v/120v wiring can be running above that window. If you run into that, then the whole job just got messy.
