Mystery Noise / Horn / Brake Issues

I have a few questions about my 03 Alero. The first, in the last few days it has started making a mystery noise one left turns. At first I thought it was a squeak, but it sustains itself all the way through the turn or until I let of the gas. The brakes are getting close to needing to be done, but it doesn't sound like brakes. The bearings were done about 10,000 K ago. It is kind of high pitched and definitly sounds like it is on the left side. Hope this description helps, what could it possibly be? And can I do it myself?

This leads me to my next question, my brakes are almost due for service. I did the bearings myself a while back and it seems I've done everything then in terms of service the brakes (with the exception of actually relpacing the pads and rotors. Am I missing anything or is it really that simple? About about servicing the rear drum?

Finally, my horn went on me. It was stuck in an 'on' position after some guy was stopped for no reason. In a panic as everyone was looking at me, I pulled the relay to stop it. I was talking with a few people and they said the horn switch is a common problem on these cars. They said GM put the horn switch on the air bag unit and they replace it all as one, costing upwards to 1000. Their suggestion was to pull a couple of horn switches off Aleros from a scrap yard and replace the one on my car. What exactly would be involved with this? And does anyone one if there is are other compatible switches from othe N bodies? In case the local yard doesn't have an Alero.

Thanks in advance.