Good news is I won't be dying from asbestos, at least for this job. I'm leaning towards a new construction window, but if I was going to go replacement window what would I do with all those channels on the side. I have 6 more windows in 3 bedrooms just like this that could use replacing. Replacement windows sound much easier especially for the other rooms. All the videos I've watched on replacement windows have what looks like flat sides, bottom and top in the area that the window will fill. With all those channels on the side there is no way to get a good fit.