In South Dakota, can my Will change my retirement account's beneficiary designation?

No!

If you haven't recently reviewed your beneficiary designations for your retirement account, you may find that your designated beneficiaries are not who or what you think it should be. This is especially true if you have recently divorced, remarried, or had children since your retirement plan was started. And while many of us make sure that important documents, like our wills, are frequently updated, we tend to "forget" about our retirement account beneficiary designations.

Remember - your retirement accounts are not part of your estate and usually are not governed by the provisions of your will, so it is important to keep those retirement accounts updated!