Welcome. Looks like you've started a good topic with your very first post. Congratulations!
My advice would be to most distinctly install electricity in your outbuilding. Electric lights are invaluable in a fur shed. I wouldn't necessarily recommend running extension cords. Depending on your abilities, you might just want to wire it up and include a couple of plugs and a few lights. If you do run an extension cord, get a high quality, heavy duty one.
Besides lights, nobody has yet mentioned being able to run a fan in your fur shed if you have electricity. Blowing a fan, and circulating air around the fur shed will greatly enhance the drying time on fur, no matter what the temperature.
Tom hit the nail right on the head when he mentioned heat verses humidity. Furs will dry okay in an unheated fur shed particularly under arid winter conditions. I dried fur in an unheated building for years. But warm temperatures don't necessarily assure drying either. I've run into stretches of 60 and 70 degree weather in the south, where hides were in danger of spoiling before they got dry. The high humidity kept them from drying, and the warm temperatures promoted bacteria growth. The only alternative is to heat them beyond where they already are to drive out the moisture. I've spent many nights in the fur shed, stripped down to my tee-shirt, and still running sweat.
Before I go any farther, I would advise folks to be
very cautious using kerosene heaters in their fur shed (or anywhere for that matter), particularly the modern “Kerosun” type heaters. The wick can screw up in these things, choke the flame down, and from there on, they exude a greasy, black kerosene smoke that coats everything like airborne charcoal. Ask my friend Jerry Chillicut. Besides, burning kerosene puts a great deal of moisture into the air, which is not a plus when you're trying to dry fur. Same goes for vent-less gas and propane heaters.
If you're asking what I would do, I'd put in the wood stove. You're in Michigan. That's a fair to middlin' cold place. The wood stove would help you dry fur, but it would also make it comfortable to work there. Mind you this comes from a man who has spent cold days on the trapline and cold nights in the fur shed. I've figured out there's nothing I can do about the temperature outside, but there's nothing in the trappers code book that says I can't be warm at night.
Like running your electricity, the better job you do installing the stove, the safer it will be. You don't want to burn the place down.
Good Luck!
-- Hal