Well I heard back from the shop today, and after doing a thorough check of the front suspension, they found that the idler arm was loose and that the wheel bearing had play. They are going to replace them for me. They also recommended that I get new tires, but I told them that I couldn't do that right now! Will wait until fall and will get some good tires put on before the winter.
Because they said that there was excessive play in both the arm and the bearings, I'm hoping that this will clear up the vibration that I'm getting.
I also posted this in the tire section, but I guess it wouldn't hurt to ask here: What is a GOOD all-around tire? Especially one that is known for good handling in snow? Is there such a tire??