Ow, about the tutorials... No, none that I know of. I'm sure they're around, but I just sort of messed about until I liked the result .

If you're any good with Photoshop (or something similar) you should be able to get decent results quite quickly. Just remember to forget about shadows and stuff like that, because Maya will do that for you! Bumpmaps tend to look really bland until you apply them to your model.

And just taking a look at other people's bumpmaps helps you to understand the technique too...