DO NOT waste money on chains or studded tires.
When I bought my used 2008 in 2011, I changed the tires to Firestone Destinations. GREAT tires in the deep snow and mud.
I live in Vermont ski country, and have never had a traction issue. My wife is a emergency department nurse in a hospital 25 miles from the house. When the weather folks are predicting bad weather, she leaves the AWD Subaru home and take the Expedition to work. We live on a private road that is usually not plowed until the snow stops flying. With the Firestones and 4 high, the Expedition has yet to have any issues.
I have a 2005 F 250 4 x4 (diesel) and the Expedition drives almost as well in the deep stuff.
On a side note, both the wife and I volunteer on the local ambulance squad (I 'm also on the local fire department, which is a different agency) and we take the Expedition to the ambulance barn when we get a call. (The Expedition's engine warms up faster than the diesel.) And we can also remote start the Expedition while we are putting on our gear.
Go with the Firestones!
marc