I need help locating and replacign the following on a 1991 Olds Cutlass Ciera 3.3 L V6: Oxygen sensor, PCV sensor and filter, and fuel filter. If you can help me with any of these and any others that need replacing please let me know. Any responses are greatly appreciated.

Oxygen sensor is located in the back manifold right before the downpipe to the cataylic converter. You cant miss it. I should jsut come straight up from the middle back. A single wire is attached to it also