Toyota Repair: 1998 toyota landcruiser codes, toyota landcruiser, cat converter

Question
I had a readout given to me for a check engine light that registered my 02 sensor located before the catalytic converter.  BANK 2 SENSOR PO 155
Where is this located?
Can I change it myself?
Does it require special tools?
I was told it needs two sensors before and after the converter, does this code mean both must be replaced?
thanks...

Answer
DTC PO155 indicates a failure of the O2 sensor on the right bank(passenger side)the one in front of the cat converter, this is the only one that needs to be replaced, you will need a special O2 sensor socket to remove it, you should be able to find it if you start looking up along the exhaust pipe from the front catalityc converter.