1998 Mazda protege LX- Oxygen sensor illustration and install
 

Does anyone know where I can find an illustration for a '98 protege oxygen sensor? I am trying to figure out where it is. Also, I have seen sensors listed as a "plain" oxygen sensor, an "oxygen sensor-Rear", and an "oxygen sensor-FRONT". Which one do I need? Please help, guys. I'm seeing codes P0421 and 0170. Is one code for front and the other for the rear sensor? Thanks in advance.