Don't part out a complete and desirable machine like this, as a worst case offer it as a project to someone.
If you can manage most of the required work and it's just the electronics that has beaten you and if you don't want to take up Daniels generous offer or maybe get someone else, like Ken or Beaky to look at them, then have you thought about one of the replacement boards available? Rottendog and KOH make some, from memory one company offers a combined mpu + driver board and the other individual mpu and driver boards with alternative interboard connectors. One of them has game selection by dips and so is fairly versatile.
The Aussie dollar is pretty high and you could flog the old non working mpu and driver boards to mitigate the costs - these go for about $30 to $40 on ebay.
If you do make the "wrong" decision and part it out I'm looking for a top left plastic.
