Andrea,
Yes, you need to document your project experience per PMI requirements in the PMI PMP application. I would create a separate spreadsheet first documenting your hours, etc.. and then cut and paste into the PMP application. Remember that all project descriptions must be no more than 550 characters. Spaces count.
I am not sure what total hours you can claim for PrepCast. Hopefully someone else on the forum can answer that for you.
Best of luck to you.
Cheers,
Mark