Some advice:
You'll need a blend of adrenaline and lidocaine, this will keep it from bleeding too much.
Maybe something to keep you from going into shock, you don't want hypovolemic shock or you'll die. Keep your legs elevated the entire procedure, take a diuretic beforehand and some benzos. Lots of anti-inflammatory. No food or drink 24 hours before. Start taking broad spectrum antibiotic 3 days before and 8 days after.
Make sure you are using a fresh scalpel for each side, coat the skin in a thin layer of iodine. Cut a quarter inch at least from the nipple or you will be super prone to infection/longer healing time. You need to be in and out of each side quickly before swelling sets in. Watch YouTube videos on cutting fascia away, only one direction and never excessive force.
Your biggest immediate risks are going to be shock, blood loss, death and creating a cavernous wound. Tertiary will be massive infection, scarring, abscess and nerve damage.