I am just starting to get familiar with Seam. In terms of introductory literature and book, as well as getting started with tools, you can go online to the seamframework site and follow tutorials there. Also, a copy of the book
Seam Framework: Experience the Evolution of Java EE.
would be immensely helpful. There is detailed information there that will guide to get something running.
For tools, you can use all free tools such as Eclipse and all the jars are free. I would recommend just getting a small web app running first, then studying the concepts after it works.