In the ED I was taught to hook up a neb set up to the O2, stuff paper towel in the mouth piece, and put mouthwash in the med cup. Works like a charm.:)
I really think you can over study. I always go to class, no matter what. If the instructor thinks it is important enough to talk about in lecture then it is probably important enough to be on the test. There is no way you can know it all.
I always use a care plan book to write my nursing dx. It makes it so much easier. Usually the care plan books include a list of problems r/t to the patient's main complaint and they even include goals and interventions.