You might want to take the coin door one apart first. So you can see what you can destroy without worrying.
Then there are a few people who are selling locks (Peale is I think and someone else, don't remember the name). They are about 4 - 5 bucks shipped each. Nice to have them all keyed together. Its worth a buck extra to have ones that the key can be removed in the open position.
And I would vote for at least the arcadevga. You can get away without the jpac.... but you will be buying a keyboard encoder anyway. So you will have to rewire, speaker hack, and the jpac has some video stuff that you can buy seperately. But I think you will find that the 'extra' price for getting the jpac instead of a ipac + extras + rewiring isn't worth it at all..
Its also VERY nice to be able to throw an original board in your machine and run it. I've passed on some really cool boards for cheap because I can't play them (when I was building my cab, no jpac, no arcadevga... It was trident3d or no windows... and I didn't want to go there... to many great windows only emulators / arcade friendly apps)