From what I can remember, first buy from Amazon under your existing Amazon account and it's already set up to you. Charge it up, tell it your wifi details and that's about it. In future you go to Amazon buy your e-books and then sync with your Kindle. I'd get the Kindle app for your laptop and phone as well. All incredibly simple.
If its the official case you're after keep an eye on the Amazon warehouse site. I got mine for £14 on there when the main website was charging £50 for it.
I can't fault the case. It's the best quality one I've found and the light it pretty good on it.
The case that i am using is a KleverCase made by The Manor Bindery. I love it, really helps give the feel of holding a normal book, is hard enough to protect it and is held in place perfectly.
I can't think of anything worse, I love the way the kindle feels and the ease of holding a single page, having it hold like a book would be, for me, a bad thing.
Still haven't found one to suit, Amazon Warehouse was £45