The plan will work. Your body will adjust and start producing the right amount of milk for the times you are now nursing. Your milk production will obviously decrease if you are not pumping while at work, but no, you will not completely dry up. I think any breastfeeding mom here will tell you that weeks, even months, after competely being done with breastfeeding, they still continued to produce milk, even just a little. (There were several months where I still was producing milk.)
Decreasing nursing can cause hormonal shifts; this is completely normal. You don't say if you have had your period yet since having your daughter, but if you haven't, it may very well resume now. Also, one other thought I had was if you were on hormonal birth control?
Evening Primrose Oil is wonderful for sort of "evening out" hormones, reducing PMS symptoms, and regulating periods. You can buy the capsules anwhere--Target, Walgreen's. Please research if you can nurse while taking this supplement--I believe you can, as I took them while pregnant--but don't quote me.