I'd recommend spending an hour at Caterham and taking lots of pictures of their cars, especially underneath and under the bonnet. I didn't and had to rely on the manual to figure out where things went. They may have improved the manual since I built mine a couple of years ago (Academy car) but there was a shortage of pictures/diagrams and some of the descriptions of where to fit parts where vague to say the least. Some were just plain wrong.
Use this forum if you have any doubts...you'll get far better answers than you'll get from Caterham and you'll probably get them quicker too. I may have been unlucky but the problems I had building my car never seemed to be during office hours!
Last recommendation...just because you can't find a part, don't assume you've lost it. There were quite a few bits missing from my kit, over and above the ones Caterham told me about (oh yes, you don't expect your whole kit to turn up in one go do you?)
Good luck!
Simon