As a couple have already mentioned, Amazon and Lulu aren't publishers - which brings up the next question, are you planning to self-publish? The process of creating the ebook itself is fairly simple - but marketing considerations add a whole new dimension to the process.
I'm currently working on self-publishing a title, so I've been scouting the internet for advice. Call me a research squirrel; I have lots of little nuggets of wisdom buried in my bookmarks list, much of them contradicting each other.
My advice would be to avoid Lulu. I've heard Createspace can be a bit harder to work with, but the cost of the book will be lower than through Lulu. Createspace also gives you easy access to the Kindle.
If you want to know about the funny details of eBook publishing, consider having a look at Smashwords: [link] .
I'm not saying that you should just go ahead and use them, but since they distribute to a variety of eBook retailers Smashwords is a good source of general (though not always particularly in-depth) information about the other places that sell eBooks. Having been using their site for a little while, I've become more familiar with which sites sell in which formats, where in the world they sell books, which retailers are handy for which reading devices...that sort of thing. They're especially handy if you'd otherwise just poke around Amazon's KDP service (and, as =vglory mentioned, there's no reason you can't sell through multiple retailers yourself).
Do be aware, though, that if you do decide to actually publish through Smashwords there are some drawbacks that they don't make clear. They're pretty transparent about how much of a cut they take from a book's sale price, but their estimates of when books will ship to retailers, when updates will be passed on, and when you'll get sales reports are extremely optimistic. Smashwords is slow. Convenient, but slow. I'd still wholeheartedly recommend using them, but depending on how much control you want over your book (and how much fiddling you're prepared to do) you may well want to deal with some retailers directly.
I've gone through Lulu on a few projects. The whole process is pretty simple, but you'll get better results in terms of layout/design if you've got more than just basic knowledge of Word. Learning how to export as PDF is pretty easy. Selling the book is the hard part.