I realize it's been a year since your post, but I wanted to make a few comments and share my story.
First, I want to refer you to the National Narcolepsy Foundation (Google it), they are an excellent source for articles, advice, research.
It has been my experience that you need to be careful who you tell. Some understand and some do not. Personally, I would not tell an employer or anyone else unless it became necessary to do so.
I was diagnosed with narcolepsy in 1990 at the age of 15. I exhibited all 5 symptoms of narcolepsy. The cataplexy was particularly bad during puberty. I took Vivactil for the cataplexy and it helped greatly. Those symptoms have diminished through the years. I now mainly struggle with the daytime sleepiness. I take Provigil and I'm closer to the pre-narcolepsy me than ever (it's what I consider normal).
Currently, I'm 40 yrs old and in my last semester of nursing school. I'm having trouble in my clinicals because the days are so long. I don't dare sit down or eat a big lunch for fear of falling asleep. Don't know how to handle working as a floor nurse.