My oral was basically a pre-flight/origination check in which we sat at a CPT and pretended we were going flying. As I checked each system the examiner would ask what I was doing, why I was dong it/expecting to accomplish, and the limitations involved. External pre-flight was done with slides...this before we sat at the CPT, and as we went through those he would ask about any limitations involved.
I did my 737 type at K&S back in DEC. The oral was not bad at all. Very straightforward and very fair. It Started by my doing a performance problem, pretty easy, follow along in class and you'll be fine. Then the FAA came in with my examiner to observe. I stood up by the charts of the cockpit and we started going through all of the lights and switches asking what they did and how they worked. If you read the smaller book they give you that will explain all of the switches and lights in plenty of detail. Your classroom prep at K&S will also be great so do not sweat the oral. The FAA person did ask me a couple of questions but they were more for discussion sake. Nobody in my class failed the oral. Good luck and relax.