There have been several posts made asking FSM for an article on how model kits are manufactured.
Hobby Link Japan (HLJ) has posted a couple of videos on their podcast site of an interview with Hiro-san and a tour of his Model Factory Hiro.
The videos are in English and Japanese with subtitles
Part 1
http://www.youtube.com/watch?v=BpH3mGRkTjw
and Part 2
http://www.youtube.com/watch?v=gqyK6u5ZTmA
Model Factory Hiro makes some high-end multimedia car kits. The process will give you an idea of the steps involved in creating such a model kit. Injected kits will be different, but much of the effort will be similar
The HLJ podcast site also has some video reports from the major modeling shows