When you said, "Noticed some items on instrument panel not working" along with the surging, I immediately thought of battery/charging system. Isn't it possible that if her alternator is not putting out sufficeint charge that the car could behave in this way?

If you are in the Norcross area, there was a great shop that I used to take mine too.

These guys are great. Mercedes Service by BMI.

http://www.google.com/local?f=l&hl=en&q=Mercedes+Service+by+BMI&near=Norcross,+GA&btnG=Search&ll=33.941081,-84.213638&spn=0.317864,0.457993