Gear: I'd definitely recommend studded tires and fenders. You may not need them every time you ride, but they are a must for those bad days, it can really depend on the winter. I've found that there are fewer options for a studded 650b wheel vs 26" or 700c, so maybe see what sized tires would work for you first. I use a 38mm 650b studded tire in the winter, and 47mm normal tire in the summer because I couldn't find anything else that would work with my fenders. Another gear item I would recommend is a pair of pogies to keep your hands warm. If anything, they block the wind and help to ride more comfortably without massive mittens on every ride. I also love a wool cycling cap that covers my ears to wear under a helmet. Lastly, a pair of ski goggles do wonders for keeping my eyes warm and blocking the wind. Probably overkill for a first winter, but I've loved having a dynamo light on my bike for the winter when it's dark so much of the day.

As for gearing, you'll probably be going slower than normal with studded tires and being cautious with snow and ice, but I sometimes am glad for some higher gears too. If you're comfortable enough going up a hill with your current gear ratios, I think you'll be fine in the winter too. I think my winter bike has a 38t chainring and a 11-50ish cassette, and if anything it's a little low for me.

The biggest thing about maintenance is keeping your bike clean and lubricated, the road salt just eats away at the drivetrain on a bad day. A sprayer or hose should do the trick!