2092 montero ceck engine light
 

I have a 2002 montero xls and the service engine soon light is on. I ran the codes and got two. Po325 which is the knock sensor, and po155 which is o2 sensor (bank 2 sensor). I'm not a mechanical by any means but I am pretty handy and I can work on older cars but not so much with cimputers engines. So my question is could I do this fix at home and if so does anyone have any idea where I should start.