A few things in regard to questions you guys have floated:
* You won't get your "section"/small group (and other course) assignments until a few days into Orientation. That way, you mix with everyone at first and don't get exclusive too quickly.
You DO actually have to "read" and sign a few forms in an official Registration session of Orientation, but it's basically just going through a line, picking up a packet, and finding out who your professors are.
* Because of that, you won't really be able to buy your books ahead of time [many professors use different books, there really isn't one set of assigned texts across different professors]. You'll have a few days post-Registration to either buy your books on campus (at the Yale bookstore or this independent book store called Labyrinth, with many of the professors use instead of the Yale bookstore) or try to quickly order them online. I'd say a good 80% of 1Ls last year just bought their first semester books at the local stores, but it's up to you - professors also have copies of the books saved on reserve in the library, so you could always photocopy the pages for the first few days, if you really wanted to order books used online.
A student group also hosts a used book sale during the first week of classes - you can generally find limited quantities of a lot (but not all) of the books you might need for your classes. Depending on your personal taste, you might find that the books available are an old edition or have lots of underlining...but in almost all cases, they'll still work and come at a great discount (I think $25 for each hardcover, $10 for each paperback?).
* Don't worry about Symplicity or trying to get RA positions any time soon. I don't know anyone who started RAing until the end of 1st semester, at least (many people don't even think about it until 2L year), and you won't need Symplicity until November-ish, when you start thinking about 1L summer jobs.
* If you've applied/been approved for all your loans and everything else financial aid-wise is in order, you don't need to worry about having a "bill" pending now. Your loans will be credited to your balance, and then you'll get a "refund" of any monies left over during the first couple days of school. If you have Qs about financial aid, I'd recommend calling rather than emailing the FA office - you're likely to get a quicker response.
In general, as you've probably noticed by now...YLS is really a very relaxed, casual place - and that includes dealing with incoming students administratively. At times it most certainly feels like you're floating without much direction, but things will sort themselves out and everything will be fine.
Can't wait to have you all on campus!