99 tahoe lt oxygen sensors

I just got a 99 tahoe lt 4 dr. 4 wheel drive police package towing package has 183,000 miles on it but looks great and runs great got it for $2,000.00
Probelm throws codes P0161 bank 1 sensor 2 and bank 2 sensor 2 not to sure which oxygen sensors I got to buy 3 or 4 wire ones and how to go about getting the old ones off I believe it is the older style but not sure how you tell the diiference.Also how do I tell what tranny it is as as what I read that would help me know which ones to buy what I see on line it could be a fl60e or fl80e can any one please help
a friend put has ob2 thing on it and says

Bank1 sensor 1 present bank2 sensor 1 present
bank1 sensor 2 present bank2 sensor 2 present
bank1 sensor 3 not present bank 2 sensor 3 not present
bank 1 sensor 4 not present bank 2 sensor 4 not present

fuel system 1 status fuel system 2status
closed loop (fault) closed loop (fault)
don't know what the above means

any help at all would be appreicated

forgot to add it is a 8 cyl 5.7l gas

problem with post cat 02 bank 2.this is the bank that is opposite side that cylinder number one is located on and post cat 02 after catalytic converter.problem with 02 heater circuit.could be a problem with the 02 heater power or ground or electrical connector or bad 02 or bad pcm or computer.chances are computer is good.would have to test power and ground for 02 heater circuit and check electrical connector out or take a chance with new 02....if high miles and original 02s then would replace.pre cat 02s are called fuel control 02s and play a vital role in fuel usage and fuel trim than post cat 02s are used mainly for computer to monitor catalyst efficiency.If high miles I would replace all 02s.if you go to autozone and get oe bosch with electrical connectors that match original.

also should be 4 wire.