171 is bank 1, 174 is bank 2
Using a lot of oil is NOT a good sign
If the O2 sensor reads too lean it will prompt the computer to richen the mixture - so a bad O2 sensor will cause the engine to run rich, while indicating lean.
This is a throttle body injected engine so it only has 2 injectors. If one is faulty and causing a problem they likely both are because both banks read lean. Most often bad injectors on these engines dribble, causing RICH mixtures.
More likely a bad FPR - the fuel pressure regulator is integral to the throttle body on this engine - and failures are not unusual.
Again, this will cause the sensor to read lean, which will cause the engine to run rich. It will also throw a 170/173 code because the mixture is not responding to lengthened injection pulse.
And you want to find out what the problem with the transmission is before spending a lot of time and money on the emissions. You also want to find out what the oil consumption problem is. You ARE going to spend more money on this vehicle than it is worth unless you have a good engine and transmission from your old vehicle and the ability to change them yourself. - or you can find a good used engine and transmission from a low mileage wreck for cheap.