This is a good questions to ask david. What I , understand from other authors.One does need a ISBN number and bare code to have a book within a bookstore. However, I don't know of authors or self-published books was accepted without at least the bare code. I have inclosed a link I hope helps with info. I hope someone who is a author or is knowledgeable than I can answer your specific questions.
Self publishers with less than three published title are not eligible to recieve a LCCN. However, they may qualify for a "Preassigned Control Number", which I have yet to figure out what that is. If you are published through a traditional publishers then they will get the LCCN for you. Here is the link to the Library of Congress website where I got the eligibilty information: http://cip.loc.gov/eligibility.html
I would like to add to Nicole's post because I have recently applied for a PCN. The PCN is for those publishers who have published 3 or less books. The LCCN is for publishers that have published more than 3 books. Hope this helps.