Remove exterior trim pieces.

With a saws-all, cut the screws that hold the unit in place.

Inside cut along the drywall and remove the drywall inside the window offset.

Verify that all screws holding the old window in are cut or removed.

Check to see which way the window is easily removed, remove the window.

Clean up opening removing nails or screws that are above the surface.

Place the window.

Using wooden spacers, level and square the window.

Secure the window to the studs.

Using pieces of drywall, finish the inside the window cavity as well as the edging. Use new corner metal.

Stucco the drywall.

Reinstall exterior trim pieces.