Lean or rich O2 codes are usually caused by something else...but not always.
A P0133 or P0153 slow response code is quite often caused by a bad O2.
If you have access to a scan tool that lets you watch live data you can compare both front O2s and see if they switch the same. The one that has slow response is usually quite easy to spot if you can compare them both.
I would still start with cleaning the MAF and checking for vacuum leaks. If those both check out ok then you're probably safe to replace the O2.
Bank 1 is the bank with cylinder #1....the passenger's side. Sensor 1 is the one closest to the engine.