It is really easy. Pick up a jack and torque wrench from Sears to make it easier. The impreza chasis is stiff enough that you can jack up the front (right behind the front wheel) and get the back wheel off the ground as well.
Its not that I dont know how to I have changed plenty of tires by myself it is just I wasnt sure about the torque level since I have never gone by that. I have always just turned as hard as I can on the each lug nut to make sure it is tight.