I just finished submitting my first book through Lightning Source Australia. The text content was a PDF export from OpenOffice (set the page size to match the print size with minimum margins as specified in LS documentation). The cover was created in The Gimp using the template supplied by LS, and then saved as a 300dpi TIFF and then converted to the CMYK colour space required using ImageMagick. It came out very well - the printed cover has less red than it looked when I tried printing here, but if anything I think the LS result was better and more accurate.
Your alternative is to contact LS and get details of someone who can do it for you. Somewhere in amongst my details here I found someone that was supposed to do it for $250 or so (but don't hold me to that).
ETA: I use LS only for printing and I wanted to be sure the print book laid out correctly, hence my preference for print-ready PDF rather than epub. My ebook versions I've submitted through BookBaby.
Last edited by gmw; 12-20-2012 at 07:39 PM.