The GIMP isn't suitable for this sort of thing.. And neither is Photoshop for this matter.
Gimp is a image manipulating program. You use it for editing photos, simple image creation, making web buttons, and such. Not for desktop publishing/layout.
For that sort of thing you want to use a layout, or in other words a DTP program. Scribus is designed for this, not for image manipulation...
In Linux:
Editing/Creating 3d: Blender (buy the book.. you'll need it. Once you get used to it it's pretty slick)
Video editing: Kino, Cinelerra (use kino)
Editing bitmapped, image creation: Gimp (or Cinepaint if you need more then 32bit colors) (what sucks for Gimp in a major way for desktop publishing is no CYMK support)
Vector based images editing: Inkscape/Sodipodi
Layout: Scribus
Basicly you make all your images in Gimp or Inkscape or whatever, and you put it all together and do text in Scribus.. (if your doing text setting in Gimp, your doing something wrong.)
Not nearly as nice as what you can get in Windows or Mac (if you have a couple thousand dollars to burn or you warez a lot), but it's a workable and has most of the peices you need. Generally with Scribus you end up producing PDF files.
Also you can do limited stuff in OpenOffice.org, it may be easier to use.
Not that I am saying that you shouldn't use Gimp for this stuff, if you like it, but it's just not designed for it. Whatever works for you is the most important thing.