DSM: Jack up the front of the car and try to wiggle the wheels, the one that has play is the bad one. I believe they are switchable, but I dont remember for sure. While you are jacking it up to see which one it is see if they have non symetrical bolt paterns.
I had one so badly worn on my 2g that it came apart on the freeway 40 miles away from civilization. It was a hot mess.