Acting tips for playing Evan in 13?

Hi, I was just cast as Evan in the musical 13. I just want some tips on how I should act as him and most importantly, his opinion on other characters. First of all, I'm 18 so it'll be hard enough playing a convincing 13 year old. I also can't sing as high as the character is written so I'll have to cover that as well. The only creative decision I've take. Liberty of is that I think he should have more romantic tension with Patrice (also the girl playing Patrice is a friend of mine and we kinda like each other). Any tips would be great though, thanks!