Ok, first the descriptions, and then my recommendations
|P0171 ||16555 ||System Too Lean Bank 1|
|P0420 ||16804 ||Catalyst System Efficiency Below Threshold Bank 1|
|P0442 ||16826 ||Evaporative Emission System Leak Detected (small leak)|
Right now, it actually looks like you have a few separate problems, but let's concentrate on the one causing the running problem. That's the P0171 code. On these cars, they're very suceptible to intake air leaks. In some cases, this is caused by a faulty air mass meter, but I've seen far too many cases of air mass meters being replaced, not fixing the root problem. The best and most accurate method of determining if you have an air leak, and the location of it, is to have the intake system pressure tested using a smoke generator. Most good diagnostic shops will have this capability. Let me show you an example using my smoke machine and the same engine you have in your car.
You'll see the smoke generator in the center, the intake air hose capped on the upper right, and the smoke hose in the lower left to introduce smoke into the throttle body.
One common leak area is here:
Often, other leaks are found near the rear of the engine, either at the turbo diverter valve hoses, or other pressure hoses.
Now, let's talk about the P0420 code. This is a catalytic converter efficiency code that will likely require converter replacement, however, wait to do that until you get the lean running code fixed, then turn the light off, and see if the code comes back.
And finally the P0442. This is a fuel vapor leak, which can also be tested using the same smoke generator, but this time on the tank and related vapor systems. I've seen many cases of the vapor purge valve hanging open slightly. I'll show you a picture of this as well.
However, none of these codes indicate to me that oxygen sensor replacement is necessary.