changing old windows out

[habsluver]

Hey changing a few windows and am upgrading from these see attached, i have measured to give 1/2 inch all around the concrete now do you think i should install from the outside and keep existing 9" interior wood frame or gut it all the way to the concrete and redo it. I have the windows coming in a couple of weeks and just want a heads up on how to go about this. Keep in mind that the 3 windows are all this old sliding style and ordered regular sliders that are parged on the exterior. Thanks