I see this question is over 2 years old so you've probably already made a decision and gone one way or the other, but for the benefit of others who come along:
There are three issues to consider:
Getting your book physically printed.
Getting your book listed in on-line sellers, like Amazon and Barnes & Noble's website.
Marketing your book.
Getting your book stocked in bookstores or department stores with a book section.
As to #1 and #2, this is easy these days. There are several companies out there, like CreateSpace, Lulu, and Lightning Source, that will print your book with a trivial upfront investment. I forget the exact numbers and I'm sure they change but they're like $50 or so depending on which company and which plan you choose. They will then get you on Amazon and other on-line sellers with little effort and little or no expense.
But these places don't do any useful marketing. Some will do marketing for extra fees, but in my humble opinion the marketing options they offer aren't very useful. It's up to you to do any marketing on your own. You can create a web site, take out ads in magazines, get a booth at conventions, go door-to-door, whatever.
Getting a self-published book into bookstores -- assuming you're not already a well-known author -- is extremely difficult. I've been on forums where self-published authors talk about the efforts they've gone to to get in bookstores, and there's lot of talk about how much work they did and how many contacts they made and how many encouraging conversations they had, but very few actually got their books on shelves. Most of those who did were people who got a specialty store to carry their book rather than a bookstore, like somebody who wrote a book on collecting antiques got it an antique shop. Frankly, unless you have reason to believe you have a special in, like your brother-in-law owns the bookstore, I wouldn't waste my time. Concentrate on other avenues. If you get to the point where readers recognize your name, then work on the bookstores.