I'm in the same boat. I thought all my work was done but USAA emailed me saying I have to call them to finalize the loan when there shoudln't be anything left to do. Oh well, hopefully this won't put anything behind. Just to be safe though I'm not registering the car until the 15th.
I know you can get some tires locally, wheels might be a problem. Vredestein makes some goos winter tires. I rodered a wheel/tire combo from Tire Rack. Ben was great to deal with and made everything super smooth. I'm not sure they could get you a set in time but it's worth a shot.