Cpt. O'Neill travelled his country, collecting and writing down trad Irish tunes, so that they wouldn't be forgotten. There are several editions of his books on the market, the biggest being O'Neill's 1001 gems. Unfortunately I've lent mine to a friend, so I can't give you any more details, such as who's published it and so on. But any music shop with a bit of self-respect should have it, or at least be able to tell you where and how to get hold of it. (Of course it won't be of much use if you don't read music.) But if you do read music, the tunes are pretty easy to figure out, and after a while you'll be able to add grace notes. Just start slowly, and then speed up as your fingers get used to the abuse.