Where there used to be a huge 10'x6' sliding door and transom in the original home, the previous owner walled it up and installed a vinyl window with extra fancy muntins - this also had to go. We had to take down the wall to install our 8'x8' door, the largest that Milgard offered.
As a reference, this is what this room originally looked like (neighbor's house):
We started from the top and worked our way down.
Was tempting to leave like this and make a "take-out" window:
Waiting to finish up with another glass transom above the sliding door. But now, when you walk into our atrium, you can see right into the dining room. We have quickly put the old window and vinyl siding out of our memory. Too bad the rest of the house is still wrapped in it, but now we know it's not difficult (just laborious) to remove the vinyl siding.