I'll just chime in and agree with the others. Slowly cut out pumping sessions. That's how I weaned nursing. I cut out the "less important" nursing sessions, like the mid-morning session, first, then the mid-afternoon, then the afternoon, then the morning, and lastly the night-time feeding. I waited about 5 days to a week between each session that I cut out. It did take a while (a little over a month or so) but, I didn't have any engorgement or leaking by doing it this way.
Simply replace any skipped breastmilk feedings with formula (or milk, or solids - not sure how old your daughter is). If she's younger and going to be switching to formula... has she had formula before? If not, try mixing your breastmilk in with the formula. First start out with 1/4 parts formula to 3/4 parts breastmilk, then 1/2 and 1/2, then 3/4 formula to 1/4 breastmilk, and lastly formula. Wait a few days to a week between each change to let her get used to it and her tummy to adjust.
If you do notice you're getting engorged, or start having pain, apply warm compresses, and make sure you're wearing well-fitted and supportive bras, even overnight. When you pump, you can try to massage your breasts in a downward motion, this will help the milk move down and help massage out clogs/and help with soreness. Also, don't stop pumping if you get a clog, keep it moving!
Good luck!