You may not even need any framing to put a window in there. It kind of depends on the type of wall construction. If you have the kind of sandwich with glass-foam-wood you can probably put in a window simply by cutting the proper sized hole.
RV windows are mostly self framing and use the wall as the filling of a sandwich. The outer part contains the glass and the frame, the inner part is the frame and the two get held together by a bunch of screws that go from the inner frame to the outer frame.
I suspect that that type of installation will also work with an RV that has normal hung glass walls or aluminum siding but not 100 percent positive about it. I would take out an existing window to see how it is put together and installed and then decide on whether to hire the job out or do it myself. Many here have done the job by themselves.
We have windows on both sides of our slideout and open them very frequently to get the breeze. That is especially effective if you also run one of the Fantastic fans.
🙂Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine