building a laptop from scratch

How difficult is it to build a laptop from scratch? I was looking at upgrading my dell (http://www.sharkyforums.com/showthre...45#post2769045). I am also looking to upgrade my desktop. But in the long scheme of things, I may be doing a lot of traveling and I needed something portable but powerful to run statistical stuff. I thought about buying another laptop but became more curious on building my own laptop for around $1200. I'd want to have a quad core with 16 GB of RAM with a 1TB HDD. Anyone build their own laptop before?