I've never pre-ordered from Amazon before, so it looks like they want you to put the full amount down on a pre-order? That's kind of wack.
Amazon charges when the item ships.
On a completely different note, I ordered a copy of Sunset Riders (SNES) today for $50ish. I've been wanting this game for so damned long and I saw it and knew it was time to get it.
Yup, they won't charge you until it ships. You'll have time usually to change shipping address, payment info, etc. If you put gift card money onto your account, it'll also pull from that for you if you want it to when they charge you. Some items also have a pre-order price guarantee where, if the price is adjusted anytime between when you buy it and the time it ships, they'll honor the lowest price that they've recorded. Usually it's only a few cents, but sometimes if you catch a weird pricing error or flash sale price, it's nice.