Rear O2 Sensor

Hey, I was able to change the front O2 Sensor on my 98 TJ Sport but could not locate the rear sensor. When calling around, I was told that it was after the Catalytic Converters but still couldn't find it. Does anybody have any tips to find the exact location and is it as simple to replace as the front sensor?

Preciate ya!

Look at the back of the cat, on top. You have to reach between the back of the skid plate and the muffler to reach it.

When I replaced mine, I had to grind a little metal off the inside of the hole to fit the Bosch sensor.