This will be my 3rd year as a school nurse so I'm still learning, but here's my input. As far as websites go, this one is very helpful and also School Nurse Perspectives is good, although it has been under maintenance recently. I also find the New York State school nurse website helpful as far as getting ideas for forms and policies.
I am contracted to work 5 days before school start. We typically go to the State School Nurse Conference, which will count for 3 and the other 2 I work in my office the week before school starts getting everything put back in place.
Supplies: all the essentials: peroxide, bandaids, Neosporin, any OTC meds you're authorized to give, bandages, gauze, tape, tongue depressors, thermometer with probes, stethoscope, otoscope, bp cuffs, etc, etc. I have a wheelchair and set of crutches, also. Depending on your school you may be asked to provide clothes for kids from time to time. At some schools, the counselor will take care of that. I do it at my school and I take donations or pick up a few items from the Salvation Army from time to time.
I am a high school nurse and really only have contact with my principal when a situation arises with a student or they need info for a report. Elementary may be a little different in that aspect. You are pretty much in control of how you run your office. You are responsible administratively to answer to the principal, but you make all medical decisions. It is your license on the line.
Difficult parents are the hardest part of the job. I am courteous and always err on the side of caution when recommending follow-up with physician, etc.
My advice: DOCUMENT, DOCUMENT, DOCUMENT. I document everything that comes through my door, even if it is trivial. You never know when the visit may come up, even if it is just the office asking if so and so was in your office at a certain time b/c they were not in class. I also always contact parent if I have any question at all. It may be something I might not consider that big of a deal, but remember you are dealing with other people's children and they may feel differently. Obviously, you can't call every parent for every visit. I'm just saying if it crosses your mind at all, let the parents know. I have only called 911 three times, but again...if I have any doubt, I call. Better safe than sorry.
I could go on and I'm sure you'll get lots more advice from more seasoned school nurses. The first year is a learning curve as with any job. You will be great. I am in my early 30s working with high school kids so I understand your concern about the respect issue. It will be fine. Do your job and be professional. Not everyone will get what you do and some will think you do absolutely nothing, but you'll soon find out that's not true at all. School nursing is different every day and you have to be ready for anything. It is a lot of fun and very rewarding. Best decision I ever made! Good luck and message me if you have any more questions. I love keeping in touch with other school nurses just to bounce ideas off of them:-)