Hi.I would like to share my experience of 2nd grade piano. I think it might not be to difficult as 2nd grade in only some foundation in piano. As I am not wrong, the test only stands for around 35-40 minutes. The first will be piano/ arpeggios(as you like, you can choose for that).Then it will be sight reading, the examier will give you a piece to play. But before you play, you can have a minute to study for it. After the sight reading, there will be aural.
I think the sight-reading is the most difficult part in the examination as you are not familiar with the piece. i think the you can request you piano teacher to practise more sight-reading before the piano examination.
Hope my advice can help you.