Sanitizing fridge and freezer after days of no power
you don't have to throw out the fridge, you just need to clean it. Forget steam and boiling water, just get a bottle of spray surface cleaner and a bunch of rags, or a tub of soapy water (use dishwashing liquid). Take out the shelves and drawers and clean them separately, then clean the inside thoroughly with your spray cleaner and/or soap. If you've used soap then rinse with clean water and let it dry. Air it out for a few hours. 

There's nothing you can do about the air circulation, but you probably don't have to. It's not as if you actually put food in there, the worst that could happen are maybe some mold/fungus spores and they won't like the dry and cold environment of the fridge. You may have some residual smells in the air ducts, those should work themselves out fairly quickly, a plate of baking soda will help absorb these although there are purpose made fridge deodorizers which are better.