About to start Insanity?!! Help! D:?

Hey I'm 16 years old i weigh 132 lbs and I'm not fat or chubby but I would like to tone and get an awesome beach body. I start the Insanity challenge tomorrow and I was wondering if with it I will actually really tone my body. I've heard Insanity is very difficult and not for beginners but do you think I'm a beginner if I use to run 5 miles a day, but now have stopped for a while since school ended. Please good answers!:) Thanks:)!