Google the egr codes and see if you can read up on the diagnostic aids for those items. Usually GM will answer the issue in the diagnostic aid section. Also because it's a soleniod and postion issue, this could be inducing a vacuum leak etc which could also cause the drivability issues.
On the wheel speed sensor. That is either a bad hub or wiring leading to the hub. These are common to our cars.
For the steering, don't worry about it. It means you don't have the magnasteering working. Aka your steering won't get firmer at highway speeds. It's a nice to have..not a must have.
