Honestly, I don't trust myself to do the modification (assuming it hasn't already been done), seeing as I've never done it...and this would be a bit of an expensive error if I botch it. Don't have much experience with that sort of work. But still, for anyone who can, that's a good link to have.
I have Pac-Man (damaged all to hell...stupid childhood), Zaxxon (decent shape), and Tetris (excellent shape, cost all of a buck!). Neat, but not much point to having them, except to show my friends as they drool over my collection :P
That's Tower of Doom. There hasn't been a Mystara on there for a bit. All that comes up (searching Dungeons Dragons Shadow as my keywords) are 3 marquees.
Speaking of which, I have the bottom half of the marquee...someone cut it to fit the cabinet. Also have the manual. Not sure how much...
Actually, it MAY have had the battery replaced. Remember when we looked at it, the stickers on the bottom were voided...means it was opened at some point. I can say I've never had it done, but I can't say for sure that it wasn't done at some point in it's lifespan. All I know is it works...