Subaru Repair: oxygen sensor, catalytic convertor, subaru forester

Question
I have a 99 subaru forester and the check engine light it on, and will not go off.  Just head the heads replaced due to over heating.  The car is using alot of fuel and bogging out, other than that it seems to run great.  I am going to attempt to change the o2 sensor myself, (front sensor)  I was looking for some instruction on how to change this, i have been looking on line and can not find a manual.  Can you give me some advice.  greatly appreciated.

Answer
Andy,

The front o2 sensor is installed at the front of the first catalytic convertor .You have to unplug the o2 harness connector and remove the o2 sensor.The rear o2 sensor is at the rear of the second catalytic convertor and is removed the same way.

Justin
All Wheel Drive Auto