There is a free download PDF of "Spring Into Action 2.0" and then there is the online documentation and references. Next there are a lot of sample spring downloads to start from......Google spring examples......This is the best one I found..Spring examples. It is a huge task to know all of spring. My recommendation is to have a basic design you are interested in , and start building a framework based on that. As you work with what you're building you'll get a great understanding of it. Add functionality as required. As you keep changing the design you'll be configuring spring like a pro once you work with it for a while. Because you can configure spring in many ways and the number of design choices are almost unlimited, it's unlikely you'll need to know every single aspect because it will not be necessary.
1) read some quick overview about dependency injection, singletons, proxy design patterns. you don't have to go very much into the details, but at leas some high-level knowledge...
2) there is a very good tutorial on the mkyong website.
these are short and smart....quite useful
3) download sts eclipse and try to remake these example
4) books (spring in action), forum, etc.