First, never ask people to hurry to help you. They are responding out of kindness and using their time.
It sounds like you used iPhoto to create the show. If that is correct, export the slide show using the File-->Export option using the 'Large (640x480)' size. First, in iPhoto, de-select the 'Play music during slideshow'.
Open iMovie 08, import the movie you exported from iPhoto using the 'File-->Import-->Movies...' option. Create a new Event to place it in by using the import options. Create a new project and drag your movie into it. Add the multiple songs of interest. You can trim where they start and end by using the little gear that appears in the to right area of the green background, which is your background music.
Keep in mind that if you want two or more songs to play their full length, the movie must be long enough, so you have to make the time each picture is on the screen long enough to make that time up.
P.S. I had to use iMovie 09 for testing this, so have to assume that the trimming feature is in 08 too. I did use iPhoto 08 for my test.