You have options. Cutting out the existing frames in one, but getting
the new stucco to match the old is often difficult. I've seen quite a
few homes with stucco that just doesn't look "right" at the windows. I
suppose you could also cut stucco very carefully and inset wood or
composite trim instead of a re stucco. Don't know how water tight that
Another option is the replacement window. Many are vinyl, at least one
is aluminum (Perma Built) and a composite window by Andersen. They all
fit inside the existing frame. Shop, shop, shop and get references,
check the web, etc....
You absolutely will get what you pay for!