I can't imagine building a laptop from the ground-up same as a PC, or even doing considerable mods to existing laptop for that matter...
One question you ask about choosing a motherboard, but the article is a barebones which includes a case and motherboard already, amongst other things (unless I misread it). I doubt there is any way to easily lookup if motherboard X works with case Y for instance just from if it fits, how it mounts and where the ports need to protrude from the case for starters. Desktop motherboards and cases follow basic standards like AT, ATX, mATX. I'm not sure there is similar for laptops?
Adding or changing components on an existing laptop is not news to me, but I thought all laptops used CPUs that were soldered to mobo, I didn't know they had user-replaceable CPUs in laptops so that's news to me, at least.
I _think_ I've seen some replaceable video cards. I know I've seen some you can add into module bay for crossfire/sli.
AFAIK, choosing or changing HDD should be easy with not very many compatibility issues as long as you get the interface correct (ide, sata) and it fits in the bay (height, form factor).
Something as seemingly easy as changing the wireless mini-pci card is problematic as many laptop manufacturers code a whitelist approved mini-pci list into the motherboard bios and no other wireless mini-pci's will work. You rarely run into that sort of thing changing PCI cards on a desktop PC.
The articles mentions limited memory chip compatibility. Using memory chip compatibility lookup on sites like kingston or corsair crucial (the two manufacturers I recommend have had the best luck with), I've never had issues in that department.
Similar to what blankcache said, I'd suggest buying a prebuilt laptop. You should be able to easily upgrade the HDD and memory. You can save money here significantly. Beyond that, make sure the prebuilt laptop has what you need.
