Yeahhhh...don't start talkin' bad about the nursery! LOL!
I just wanted to say that you shouldn't be so hard on yourself, or have such high expectations! Guess what? And I'm TOTALLY serious about this...You don't know ANYTHING. That is a fact. What we learn in nursing school is an ice chip off the iceburg that sunk the Titanic. No one expects a new grad to waltz in the door and function unassisted- you're there to learn! The only way you become a competent, confident nurse is through experience. Period. A degree and a license is worthless without experience, so don't feel bad!
You said they're notoriously hard on orientees? GOOD! That's actually a good thing. It won't help the butterflies in your stomach and it won't mean much to you at first, but in retrospect you'll become so much better at your job if they challenge your knowledge and help it to grow instead of giving you minimal information and throwing you out there on your own.
You won't disappoint them- you've already made an impression and they KNOW you're new. Take advantage of it- ask tons of questions about everything! They may not be able to answer everything, you will have to look up quite a bit on your own, and when you do, take that new information and tell them about it. If you're worried about making a good impression as an actual nurse, I find that studying relevant topics and discussing them with my co-workers is a great way to open the door to mentoring (your preceptor might not be great, but you might find another nurse who will take you under their wing!) and also helps to cement what you're learning hands-on.
If they are showing you something, ask them if you can do it. Ask them to walk you through it instead of standing back and watching them perform it. Ask "Why" a lot. And finally, compliment those who go out of their way to help you, because eventually you may find a friend and confidante in these people, and at the very least, it makes them a bit more willing to help you. Bringing food helps, too.
Good luck, and congratulations on getting your preferred placement! L&D is exciting!