Firstly I'll say Keep it original
! You post actually made me grimace when you said what you wanted to do
. Don't put a f**king TFT in there what ever you do and don't put a f**king Multi-Driver configured PC in there.
But I figure you're past that and want to go the emulation route.
So if you
have to make it into a multi-driver cab, here are some things you should know.
http://www.ultimarc.com/JShopServer/
This place sells everything you will need to interface your cab with a PC. Don't go the XBox route. It's actually more hassle for less satisfactory results.
Buy a second hand PC of eBay to the spec you desire and then get a couple of things from ultimarc. Get an APAC. This is a USB interface that will allow you to connect pedals, wheel and buttons to your PC in one device. Then get the Arcade VGA Graphics card. This will allow the computer to work on your arcade monitor either low res 15KHz or medium res 25KHz. There's also loads of info on that site for wiring etc. The guy who runs it, Andy is also a legend and very responsive to questions and stuff.
Then buy some molex connectors and wire it such that you can plug in all the PC stuff, and use the cab as you like. Or unplug the PC and plug in all the original hardware. Simple, no
hacking, no
butchering. With the people here, you can probably have the sound issue sorted in no time on that original board, and leave it fitted in the cab. Then you can take the PC out if you like and return to a dedicated S.C.I. in no time at all.
Don't touch the artwork unless it's to restore it with reproduction stuff or very well applied, minute amounts of touch up paint. So what of it's got some marks, it nearly 30 years old, what do you expect. Live with it, it's the cabinet's unique soul. It's lived a life and doesn't necessarily need a full cosmetic make over to have new life breathed into it. Give it a thorough clean, maybe respray the pedals. You'd be surprised at what a difference just that makes.
Anyway, don't be afraid to ask for help at any stage. The last thing anyone in the arcade collecting community wants to see is a pulled apart S.C.I. with an XBox and a f**king TFT in it. And I used to think like you once upon a time. But believe me, if you want that feeling you have when you played on these cabs originally, stick with the low res arcade monitor. You won't regret it.