http://teampronto.com/?page_id=318
These are the material we used to teach our students this year. They're a bit on the incomplete side in terms of Java and WPILib basics (because most of that was done hands-on), but the setting up your workstation part (which can be hard if you guys are new) is fairly detailed.
IMO, the best way to learn code is to read it. After you follow the instructions to install the WPILib modules, you can start an example FRC project, and try to understand what the code is saying. I personally don't quite get command-based and its benefits over standard coding, but some teams I've spoken with have said it's easier to start out.
The overall learning curve should be shallow; we taught and had freshman students successfully coding kitbots, previous years' robots, and almost every actuation feature within 40 minutes after we taught them what Java was. Other things (advanced features, PID, vision...etc) may have to wait though.