B2S1 / Bank 2 Sensor 1 is on the passenger side exhaust manifold.
Sensor(s) 2 are downstream from the catalytic converter.
P0055 is a code for B1S3 which your truck does not have. P0052 is for the heater circuit on B2S1 -- this is probably what he meant, and it is common on your truck -- the heater will degrade over time.
Use only the Nippondenso sensor for your truck, and I recommend the dealer - you can order them in a 2 pack, do both sides and save some money; if the heater on Bank2 failed, then Bank1 is probably right behind it. Absolutely no Bosch, or other aftermarket sensors. Get the right sensors that fit and perform properly in your truck... plus Toyota has updated this part, so the new sensors should last longer. You wont save money doing it twice.
You're going to need a 7/8" Oxygen Sensor socket, some penetrating lube to remove, and some anti-seize for the install.
Good luck, and I hope this helps.