ER found a mass on an ovary last night...?

Your ovaries continue to work even without a uterus. It is NOT better to get your ovaries removed and go on hormone therapy. Fake hormones are not as good as the real thing, and your health and quality of life will suffer. A better option would be to go on birth control pills. They will suppress ovarian function (but the ovaries will still work somewhat so it's better than using fake hormones) and therefore suppress any possible cysts you might have. However, if you have a "mass" on the right ovary, they might want to remove it. But you should keep your left ovary.