You could see -20f which is fine for OEM fluids but if the vehicle is new to you some fluid changes is a good idea anyway.
I would change the antifreeze or engine coolant. You can do that yourself and that way ensure you have the proper mix (50/50) or you can measure the mix with a coolant tester. Windshield washer fluid should be used up and replaced with -40 rated otherwise that freezes up and you'll have to wait for a warm day or find a warm place to park to unthaw. You can add water to the -40 stuff if you run low, depending on how cold it is of course.
Synthetic motor oil will be nicer to the engine.
As for tires, that's a personal preference and depends on how the vehicle is used. I like studded narrow snow tires but not worth the extra expense or hassle if I'm spending most of my time on cleared paved roads, which will likely be your case. Consider Blizzaks, X-Ice but they, and an extra set of rims, may not be worth it as there are several tires that are pretty good for year round use. Lots of reading to be had on that topic.
You will want a block heater. If it was the north coast of Alaska more than one with a circulating heater would be great but all you'll need is one and they really do save engines. I've seen more than one northern engine where the condition of the cylinders were best near the block heater with the worst cylinder, the one resulting in the rebuild, being furthest from the block heater.
Electric fans are nice on cold winter days. Engines do warm up faster without blowing -20f air across them but not worth upgrading unless you were already doing cooling improvements.
And you want everything like the cooling system to be working well. A leaky or poor thermostat may not be noticed until the cold hits and the engine doesn't warm up and as a result the cab is freezing and you have to drive with an ice scraper to see out the window. Also getting stuck can overheat the engine if the cooling system isn't working well, though at -20 it's easier to cool it off by opening the hood.
And don't forget yourself. A winter kit should include extra clothes. Some get a pair of insulated coveralls and leave them in the vehicle with extra gloves, hats, even boots if you do not usually wear good winter boots. You can clear a lot of snow over a few hours but not if you are wearing sneakers and a baseball hat and it's -20 with a nasty wind.
Of course you'll not get it right the first winter because you do not yet know what you will be dealing with so I'd say prep a bit and then start a list of what you would have liked. Do that and you'll be better prepared in your 2nd winter than many who have spent a life time there.
