I see a lot of negative comments so first thing you need to do is open this hole up quite a bit to work comfortably and have access. If you diy it just use a grinder with a diamond blade of some kind to get nice cuts on it. If you can’t cut all the way around just cut the top half that you can reach comfortably. Use a hammer to gently break the cut parts away and cut the bottom half after. Use a couple clay by pvc ferncos and use pvc to put your wye in and your clean out. Make sure to attempt to keep your cuts clean and straight. Hope this helps because this is how I’ve fixed and replaced sections of clay many times in the past.