That's wonderful that you're not afraid to have your mastectomy. From what I see re your diagnosis, it seems as if it might be caught early? I'm fortunate in that mine was as well, but not as early as I believe yours was because I had invasive breast cancer. Hopefully, you will be fine from this experience and if you have faith and belong to a religious community, that will stand you in good stead in helping you get through this time.
I wish you a good and peaceful week before you surgery and a safe surgery and pain free recovery. If I can do anything for you, please let me know-I'm a Librarian (retired) and also a trained Medical Librarian.