RockyMtnHigh pretty much hit the nail on the head. Any nagging issues in normal weather can be a big problem in Cold weather.
55/45 on the Antifreeze is a good recomendation, but truly not required unless you plan on going north of Saint Paul. A standard 50/50 mix will work fine in Saint Paul, though you may get close to testing the limits
Make sure all the hoses in your cooling system are in good shape as well. Amazing how many of them fail in below zero weather.
Make sure you drain out (or just use up) the windshield washer fluid in the reservoir before winter hits. Having lived in a warmer climate then come back for christmas, having a blue ice cube in the reservoir sucks. Get the good stuff rated to at least -25F.
A winter survival kit is a must. Blankets, extra hats gloves, etc... Jumper cables. Candles and something to light it with. Some energy food - energy bars, granola bars, candy bars... whatever. A shovel is generally not a bad idea, and I have used my tow strap and recovery equipement more than once to help others in a jam...
Good luck - most of all, make sure you actaully try to enjoy the outside weather. Its too easy to become a hermit in the winter. Go outside and ski, snowshoe, ice skate on the outdoor frozen rinks, snowmobile, ice fish, whatever. It makes life much more fun!