Create Book Cover

We are creating a children's book. We are not having it professionally published, but going through a service online to print up the books and we need to create the book cover (front, back and spine). The service has given us specs as far as the dimensions, dpi, colors etc. We had a friend create one the best she could, but it just didn't turn out very well. We have an idea of what we want and are hoping someone can expand upon it or at the very least just exactly duplicate it, but in the given specs for printing, which we don't know how to do correctly. We created a version in PhotoShop which approximates what we want but, of course, it's not the correct resolution as the background image is from the web and is at 72dpi. I have attached a PDF which is the one our friend did. This is using the correct specs, as far as I know, and is how it should look as far as the layout front, back and spine, but we don't like how it turned out. I also attached a small JPG file which is a version of the front cover that we did. We want something along that line but made into a PDF or PSD with the correct specs. We still need the words, logo and barcode (all of which I can provide) on the back cover, but we want the front cover to look more like the JPG. We want to keep the theme of the night sky, the moon and especially the butterflies. Like I said, you can do exactly what I did or come up with something even better. We don't have a lot of money to work with. I'm hoping this will be really easy for someone to put together real quick as we have already made the website to sell the book (mainly for friends and family) and will be trying to get them printed in early October so we need this cover done fairly quick. Here are the specs given to us by the printing company: 4 color process. Bleeds: Full Bleeds / 1/8" Bleed must be included in file / no type or borders within 3/16" of edges. Resolution: 2400 dpi. Halftones: 175 lpi. The size of the book is 5 1/2 x 8 1/2. I will provide you with the image of the girl, the barcode, the Believe Publishings butterfly logo and the verbiage that goes on the back of the book. THANK YOU VERY MUCH FOR YOUR TIME. This is for a good cause. :-)