Replacing Picture Window

I have an older picture window that is approximately 50" (tall) x 90" (wide) that is double pane and has gotten dirt in between the panes. On either side of the picture window are a double hung (approx. 12" wide, same height). It looks like all that is between the double hung and picture window is a 2x4? Anyway, it will cost approx. 400$ to get the picture window replaced (installed price) and probably 250$ to replace both double hungs. I've been thinking about replacing everything however with a bow window slightly smaller than the entire opening... I realize this will require replacing some siding on the outside and retrimming the inside... My concern however is can I remove the 2x4's that are between the picture window and double hungs? How do I know if there is a header above the whole unit without removing a bunch of plaster and tearing into the inside wall? Do I need to remove outside siding (wood siding) to find out. Or am I just better off replacing the window with similar units/styles?

I can purchase a bow window at the local building/supply for around 650$ that is just slightly smaller than the current opening.
Thanks

 

It probably ISN'T a 2x4 between the picture and the double hungs.....most likely you are looking at the side jambs of each window where they were mulled together and covered with a small strip of moulding. The side jambs are usually 3/4" lumber and together they would look like a 2x4. Look for the thin cover moulding and pull it off to see if I'm right. Genenrally, the individual windows were joined together with some corrugated strip fasteners along that side jamb, but I have seen them with an inch or so of just blank space in there. ( less commonly)

You can then pull the casing off the top of the window and see where that mulled section joins the header pc of the window frame...there should be gap between the top of the window frame and the house header....if there is, then the house header is continous across the opening and no pressure is on the window, meaning you can do whatever you want with the opening. IF there is actually a 2x4 in there, you will see that too at that point and know you shouldn't take it out, as it is probably load bearing.....or then go outside and pull some siding and sheathing to see what you have for a header.

As to window replacement types, once you get a handle on the header, you can decide what to put back in.

 

Thanks - I pulled the inside trim off and you were right. It is just the two jambs up against each other - actually there is about 3/4 inch of space in between the jams with insulation in there. So... that means the header would go across the entire unit, correct? I priced a bow window last night for 670$ or I talked to them about putting 3 big double hungs next to each other. They said you can attach them together without having framing in between them... wonder how efficient that becomes?