The oxygen sensors can be replace easily.
Before getting started you want to make sure that the engine is cool so you don't get burnt from the hot exhaust.
You will need a oxygen sensor socket to perform this task.
Here is a helpful guide on how to replace the sensor:
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.