Though rooting gives you full control of your device and you can modify a lot of stuffs like the theme of your phone and tweak something to your phone performance such as its battery life and CPU clock speed (as far as I am aware to some devices). If one is really enthusiastic doing it for the hobby, s/he should just do it in another device that does not contain any sensitive information.  

@OP, like everyone mentioned in here, better get that unrooted first before you attempt to do anything that would involve your money. Reformatting won't unroot your phone. You either need to flash your stock ROM from the phone's manufacturer or use a dedicated rooting tool which I used back then from my old dead phone. Just be careful though as the process might brick your phone like Lucius mentioned, but it should not be a problem as long as your phone has plenty of battery power and a reliable USB connection.

This is quite nice to know. Back then, I did not install any apps that would involve my money so I was not sure. Either way I might not install one anyway since I am scared to brick my phone and lose access to my banking apps.