Math in Nursing

I recently been accepted into a BScN program and will start this fall.
I was wondering how much "mental math" is usually required in school and the profession...

I'm a very visual learner and have to work out math with pen and paper. Also for the past.... decade or so i've become rusty with mental calculations (yes +/-/x and division) as I now rely on the calculator.

Will my calculator dependance and visual learning style hinder my progression throughout school? Should I spend my free time, now, before school practicing calculations in my head and conversions etc?

Does anyone know of a good practice book?