For page layout and design, I use Adobe Creative Suite (InDesign, Photoshop, and Illustrator CS5). In this age of digital presswork, it no longer costs an arm and a leg to have a four color book cover. I can design and lay out any kind of book or jacket cover you can think of, using your artwork or artwork I can find (I usually look for copyright-free and royalty-free elements, but occasionally there are fees to third parties involved). It's always better if you have a definite proposal of what you want on your cover, but, if you only have some general ideas, I can work up two or three possibilities for your approval. Take a look at my portfolio to see the sorts of book covers I have produced for my clients over the years.
People don't always give a lot of thought to it, but text design and typography (fonts, font size, chapter heads, running heads, page numbering, margins, paragraphing) are important factors of your book's appearance. When a client submits a manuscript, I ask that he or she send me both a MS Word document (digital file) and a hard copy print-out, so that I can get some idea of how that client would like the text block to look. If you're not sure, I can work with you to get a look you would like. And don't be afraid to say "I like the way the text appears in such and such a book." While we don't want to copy anyone else's creative work too closely, referring to books you find impressive or attractive is a good way to get going on your own ideas. The same goes for book covers.
Editing, design and layout charges are based on a hourly rate. Your contract will specify a maximum amount that these and other services may require, and I work up to and do not go over that amount (assuming the original terms of the contract have not been modified by you).