Is surgical removal of a multicystic dysplastic kidney a cure?

Probably yes. I assume the other kidney is normal and if so removing the diseased kidney reduces your chances of having infection, hypertension and malignant trasformation. You can live a normal life with no restrictions with one kidney.
Yes but ? necessary. Majority of multicystic dysplastic kidneys involute spontaneously & thus do not need to be removed. V. Rare large mcdks which affect a baby's breathing are best removed asap. Others can be observed with follow-up us 3 months after birth, then 6 - 12 months later, then annually till gone & only removed if increased in size or haven't shrunk. Negligible risk of tumor, infection or hypertension.