Thanks for breaking the ice, Lori; I was trying to figure out a polite way of saying, "You really aren't going to equip yourself from Amazon, are you?!"

In the original post, you don't say where you live; but since it's only 2-3 nights you're planning, I'll assume you live near where you're going, which puts you somewhere in the Northwest. That means there's a good chance there's an outdoor shop near you (perhaps REI, or maybe a local outfitter.) Buy your stuff there. You have to really try hard to buy lesser-quality outdoor gear nowadays, but if you're dead set on getting the heaviest, least useful gear you can find, Amazon would be a good place to start. (Dick's, Gander Mountain, Pro Bass, and WalMart are also places to easily go wrong.) Don't get me wrong; these places also have some good gear, but they have a lot of marginal and unsuitable gear for backpacking.

The outdoor store will carry a better range of gear. Yes, their sleeping bags and packs will cost more than the stuff on Amazon - there's a reason for that: quality. The outdoor store will also have a knowledgeable staff that can quickly tell you what you do and don't need, and how the pieces come together to form a good kit. They'll be able to fit your pack to you, which, as Lori said, is vitally important; they'll also be able to help you pick the proper capacity pack. You'll pay a bit more, but you'll be way ahead in the long run, because you won't be replacing the bag, pad, etc. right away and because good advise from people who know their inventory is worth a little extra money.

One specific comment: while the Katadyn filter is a good one, it's probably overkill for anything you'll be doing. Take a look at the MSR Miniworks. It's cheaper, simpler to use, reliable, reasonably light (but not ultralight) and consistently gets high marks (well, maybe not from SkateboardJoe on Amazon, but definitely from people who've spent some time actually using it in the backcountry.)

Do some research on gear lists here, then print one out and head to a reputable backpacking & camping store.