Actually, it couldn't be simpler to screw a motherboard into a case. And strange as it may seem, someone doesn't really even need to know what a card actually is or what it does to install it. All someone needs to do is install a card in the correct type of slot (AGP/PCI/ISA - though if it's a newer motherboard, it's not very likely to have ISA slots) and it's pretty much impossible not to because the card won't line up correctly otherwise. And if one is simply switching a card from an old motherboard to a new one, all they need to do is install the card in the slot on the new motherboard that looks just like the one on the old. And so far as reconnecting any cables on, say, a sound card, simply take note of where they were disconnected and then connect them back in the same spots. No biggie. RAM strips are even easier to install. Hard drives are easier still. And once everything is in place, the motherboard's own BIOS should have no problem whatsoever identifying what's what - and it will communicate that info to the operating system once that's installed.
In my experience, the only problems that might arise would be with installing Windows. True, installing WinXP is light years ahead and much simpler than installing Win95 or Win98 ever was, but it can certainly still be temperamental. (And if you ask me, the Windows operating system is ALWAYS going to be temperamental. MIcrosoft will never get their act together when it comes to that!
) Though even the most temperamental install can be straightened out by following the advice that Windows itself provides the user - most notably in the Device Manager area. Microsoft's Windows support techies might like to make it seem as if they're ALL-KNOWING. But the truth is that the only thing they might have on you is more experience. The simple and unvarnished truth is that there's nothing they can tell you that with a little investigation Windows won't actually tell you itself.