This video is very usefull for introducing most concepts of c++ in about an hour. The sample programs included in the software is a good resource as well. Most of your work will be looking through the WPILIB documentation (at least it has been for me). I wouldn't say the languague itself will be particularly challenging if you have some experience with any other programming language. C++ is pretty expressive (means you can read the code out and it sounds somewhat like english). Good luck!