Hey Cassidy,
Per your recommendation, I bought Arcadeshop.com's MCR power supply kit and got it installed today over an extended lunch break (you may have noticed my rear end hanging out of the cab here: http://www.thinkgeek.com/images/cams/kitchencam.jpg).
I didn't use the snake-bite AC power connectors they included with the kit (no mention of them in the instructions...maybe they were for grounding, on second thought?! I'll email them and ask). I just soldered and bug-nutted two wires from a PC power cable between the new power supply and the main AC input for the cabinet (which I had already replaced, since my cab came without a ground prong...eep). I also couldn't get the little screws included for mounting the PSU to grab it, so I improvised the mounting.
The good news: it powered on with no trouble, and after beating the default 2000-pt high score, it saved the new #1 score and 1UP score through power-off and unplugging...w00t!
Only time will tell if the sound fades intermittently...
Thanks again!
Jacob