Hi, I want to ask where the front and rear O2 sensors locate in an Hyundai 2000 Accent GL? I found some sensors with 2 or 3 or 4 wires on the internet. Some of them are heated, some are not. I don't understand what they mean. Which one should I buy? It's said it's pretty easy to replace them by myself. Is it true? What tools do I need?

Thanks a lot!

Cars & Trucks - Hyundai - Accent - 2000 Hyundai Accent