For reference, forum user PaulF was the one that did the 12V conversion using a 25-dollar part available on mp3car's store. He documented it here: hhttp://paulfurtado.com/hacking-sheeva-power.php.
The formatting came out a little squiffy. But yay! I really cannot thank mp3car enough for this thing.
I posted some other pictures here: http://icculus.org/~chunky/sheevapics/, but I can't garauntee they'll be there forever.