I am installing a new dishwasher in an investment property I own and have an extra 30 amp breaker that the previous owners used for a lets say "interesting" wiring arrangement(one that cost my home inspector an expensive tool and almost his life. Is it OK to use the 30 amp breaker for the dishwasher, the wiring book I have says 20 amp but I don't see anything that says I can't use it instead of a 20 amp breaker.

I'm definitely not an expert, but...

I would think it wouldn't matter if you used a breaker with capacity above what is listed.

Just make SURE you use wiring that will support 30 amps, off that breaker. Otherwise, if something DOES manage to pull over 20 amps on that circuit and the wiring can't support it, the jacket might melt, and you could have an electrical fire on your hands.

It is only acceptable if you run #10 wire. Come on, the 15-20 amp breaker you need isn't that much.