Surprisingly, there is only one small window to deal with in this whole project. We built 30 years ago with 9X4 vertical seam sheet masonite siding. Last summer I pulled that off the front and back, replaced it with 3/4 inch plywood. (Bottom 2 feet green treat, upper exterior) I followed that with house wrap and Moderra split face "brick look" block product. I wrapped the brick around each corner 2 feet, so I am left with 13 squares of basically blank wall to vinyl side. I am furring it out because the wrap around brick sticks out 2 1/2 inches from the old masonite. With the furring it will stick out about 1 inch from the highest part of the siding.
Since I am not breaking into the old wall, I figure if I bring the house wrap up to the one 3' x 2' window involved, I should be OK. The house wrap is cheap, and I figure it will not hurt. We built before it was common, so we did not use it the first time around. Presently we have the 3/8" masonite, 1 inch foam board, 2x4 stud wall with R15 fiberglass, 1 inch foam board with foil both sides then the drywall.
Will add house wrap, furring strips, vinyl.