Help! with Graphing Calculator?

Last year when I started Pre-Cal, my dad gave me his graphing calculator that he used in college. It was around 20+ years ago, since he bought it. This year I'm in Calculus and my teacher recommends using a TI-83 graphing calculator. Should I buy the TI-83 instead of using what my dad gave me? My dad's graphing calculator model is a Casio fx-7000GA. I don't really know how to use my dad's, only a little.