I want to start off by saying that there is no way you will fail, even if you don't have anything working when you get to your first competition, other teams will go out of their way to help you, all you have to do is ask.
However, it's hard to help without knowing where you are stuck, I'll give you some helpful resources, but you'll need to do a good bit of reading.
First I would suggest going through all of the info here:
http://wpilib.screenstepslive.com/s/3120/m/7913
This is a good reference, you don't need to know everything about C++, but it's a good idea to at least read up on the basics to help you get started:
www.cplusplus.com/tutorial start with just the basics and control structures sections; and read on as you feel the need.
If you've got more specific questions, just ask
