P0161 O2 sensor code???

[bass_caster]

2000 new body style tahoe 5.3 v8 4x4 automatic with a/c

a couple days ago while driving the service engine soon light came on. my brother-in-law had a code reader and came up with P0161 heater circuit bank 2 sensor 2. from what little i found about that code online, it sounds like an O2 sensor issue. the information i found is conflicting though. one place says bank 2 is drivers side, while another site says bank 2 is passenger side. both say sensor 2 is downstream of the cat. so i have a couple questions...

1. i just want to confirm which side is which.
2. how many total O2 sensors are there on this thing?
3. what are the odds that its actually the O2 sensor and not a short or other issue within the system.
4. last one... if there are more than 1 O2 sensor, are they all identicle or is each one a different part based on its position?