Your spouse could be entitled to part of your personal retirement plan if you get a divorce. However, you probably only have to divide the portion you learned while you were married.
Furthermore, Minnesota courts would probably not require you to divide your assets completely in half. There are many things that go into asset division, among them being each of your respective contributions to the asset in question, the portion that is marital property and several other factors.
In fact, after you determine what portion of your retirement accounts goes to each of you, then dividing the funds per your agreement is significantly less complicated. However, there is some paperwork you may have to complete and you may have to involve third parties, such as attorneys and asset managers, to ensure the transfer completes smoothly and you do not incur any undue tax burden.
The exact type of your retirement accounts also will play a role and how you divide the assets after you reach your decision. As per the IRS page, 401 (k) plans would probably require a qualified domestic relations order directing your fund manager to distribute the money to avoid early-withdrawal fees and taxes. IRAs and other accounts may not have the same requirement, but you would still want to transfer the funds correctly and at the right time to avoid a tax penalty.
One of the most complex processes you would encounter in a Minnesota divorce is likely to be asset division. Please do not act on this general information. Legal advice should be specific to your unique case.