O2 sensor DIY?
 

I wasn't sure if this fell under header/exhaust or fuel system, so I put it here. Anyway, my eclipse has code error p0135, O2 Sensor Heater Malfunction, Bank 1 sensor 1. I don't know which O2 sensor that is or exactly what the issue is. I figured replace the O2 sensor and see what happen. Wondering if anyone can either tell me where the O2 sensor are located (I believe 1 on the manifold and 1 right before the cat, but if there are more, pray tell) or if you know a better fix for the issue. It's a 2004 eclipse gs.