Yeah - I've done some more researching since posting, and you're both exactly right. I did find this:
http://www.ebay.com/itm/LCD-Controller-board-for-DIY-a-...
in case anyone stumbles across this and is intent on doing it. It's a controller for a laptop display, so it can be used as an output for another computing device. I assume I could find something similar for the keyboard and mouse (or cannibalize controllers from external keyboards/mice) but I figure that would push this project into the $100+ range, and I'd have at least 3 power cords running to the laptop, or some significant electronics work to be able to use just one. At this point, I'd rather just, as you say, give up.
Thanks for the help guys - I really appreciate the responses.