I crawled around underneath the car, and it looks like the subframe bushings have seen better days. How difficult are they to replace? I'm leaning toward having my mechanic handle it, but if it's easy perhaps I'll tackle it.

I wasn't able to tell anything about the ball joints. I'm thinking about having them replaced when the car is in for the subframe bushings.

One observation -- I drove about 600 highway miles this weekend. At times, the car drove perfectly, and at other times it was doing all the things it's been doing. Any idea why it would vary?

Thanks,
Mike