You can get almost any kind of gearing you want. It depends on the type of cranks you have and the bolt patterns. Also on some cranks the chainrings are bolted together which means you can't change them. You would need to buy a different set of cranks with changeable CR's. Your local bike shop (LBS) can advise you either way.

Welcome to biking! You'll find a bunch of kids here in their 60's.