Full .pdf of the finished result is here: http://www.summerblock.com/Ikea_Baby_Book.pdf
Step 1: Gather Necessary Software, Etc.
--3D modelling software; I used Google Sketchup Pro and 3dsmax
--A handful of Ikea instruction manuals in .pdf, available here: http://www.ikea.com/ms/en_US/customer_service/assembly_instructions.html. Pick ones with similar layouts to the manual you want to make.
--Fonts; I had good success with Twentieth Century Modern throughout (bold-faced for the title page). Oddly enough, the Ikea Sans font that comes in the online manuals doesn't look quite right to me. I was using an actual manual that came with my bookcase for comparison, and the capital A on the cover, in particular, was hard to match.
--A 3D model of the object you want to assemble. Either construct it yourself or Google "free 3d model _" and fill in the blank. I was only able to find a baby model in Sketchup format, but then I exported it as a .3ds and used 3dsmax.
--A liberal interpretation of copyright/trademark law. Hey, it's satire!
Step 2: Sketch Out Manual
After you have a rough idea, think in particular about what kind of images you'd like to use--which parts of the model from which angles, etc., and make a list of all of these.
Step 3: Cut Up Model and Capture
Now, by turning the slice planes on or off, you can isolate the pieces of the model and render images.
If necessary, open the images in Photoshop and adjust contrast and brightness settings until you have something that looks decent. Remember, it's supposed to look like an Ikea line-drawing in the end.
It's possible that by using something like the Illustrate plugin for 3dsmax, you could make a more convincing line-drawing, but I wasn't able to get it to work. Instead, I just turned the contrast all the way up and the brightness down a bit in each image; I was satisfied with the end result.
For help with 3dsmax and other modelling software, check out this website, with lots of helpful tips and video tutorials: http://designreform.net/
Step 4: Make Layout
Since Illustrator can only export what's in the "art board" as a .pdf, I made one large Illustrator file and several rectangles the same size as the art board. Then, with guides, I could make all the pages look consistent. Once you're done with all of your pages, you can drag the whole thing around until each page is on the art board, then save that as a .pdf.
Optional: customize the "preamble" pages at the beginning. I used one with written instructions translated into 18 languages, and I changed the word "wall" to the word "baby" in each, with the help of a polyglot friend. Also, I remade the cartoon characters to look more like my friends.
Step 5: Finalize Layout and Print
Fold the pages, staple, and enjoy!