My $.02:
* It seems to me doing your normal walks on days you run, if that is what you'd like to do, would be just fine.
* Overall I wouldn't get hung up with Chi Running right now - at least not the details. The principles of run tall, short strides, "falling forward" I think are good to think about some when you're running - at this stage. But beyond that it seems to me your brain could get overloaded pretty quickly - since you're also dealing with C25K timings and such. The things I mention are pretty common to all of the "packaged running forms". The other components become unique to different programs and are the finer points - and consequently take more concentration - than the major ones.
Have fun!
Jim