Is the board actually booting when you have these problems? Come up to attract mode with the playfield lights blinking, start a game, etc. even though the display does not work? Is the LED on the soundboard blinking as it should be when you are having sound issues?

Please respond with that info, as it makes a huge difference as to next steps. Figuring out the display issue should be fairly straightforward - the sound card might be a little tougher.

You have a multimeter and comfortable measuring voltages? It will be necessary to diagnose the problem, so get yourself up to speed there if you aren't already and we'll try to get you fixed up.