Tonichelle, If you haven't been to a comptetion before I would definitely recommend going even if you don't have "great" tickets. It's a wonderful experience.
First off, if you are going for the week, I'd recommend all event tickets. You get to see practices with them and they are fascinating. You get to see the skaters in a much less formal setting and can sit much closer to the rink. They typically dont sell practice passes separately. However, if you are only getting single event seats, you can often get into practice by volunteering at the event. That requires a significant time commitment, but is a great way to see the "inner workings" of a big event.
Even if your seats aren't too close you will still enjoy it. During the early events, you may be able to move into an empty seat, but even if you are higher up, seeing an event live is completely different from seeing it in person.
Definitely talk to the people around you or the people you meet at practices. Generally the people I've met have been very helpful and willing to explain things to me.
I'm sure if you bought your ticket now you could get a fine seat, but there often is an advantage to waiting and getting one from someone else so you know just where the seat is. I think you'll be able to get a perfectly fine seat whenever you order. Sometimes good seats open up closer to the event when sponsors release some. However, I wouldn't worry too much, youll have a blast wherever your seat is.
One other tip, be sure to get sleep before you come! There's not a lot of sleep during Nationals.