What sections should I include in the Project Description section of my NSF grant proposal?
The NSF doesn't specify any rules on what goes into the project description, but each community has its norms and expectations. If you wish to get a good review, it's probably a good idea to understand the norms and standards of your community.

In general, what you should do is find peers in the area that have written proposals for this program and look at what are standard templates (and isn't your advisor involved in this ? In my corner of the NSF, students can't be lead PIs on proposals). 

From the sound of it, you haven't seen too many examples of proposals (successful or otherwise), and I'd strongly recommend that being your first step. If that's not possible, talk to faculty within your department (again, where's your advisor ?) to get help.