I have a MY2011 Eos and the 'Fault in Catalytic Converter' warning light has been on for quite a while, (15,000km) with no obvious deteriation in performance. Automasters have identfied it as the rear O2 sensor not working. I am wondering is it really needs to be replaced, and if so is it a simple job to do oneself. The local Automasters are estimatig AUD600+ and it seems the part alone is ca.AUD400 if I buy it through the VW agent. It seems I can get the part online much cheaper but I am not sure of the precise part no. Any advice appreciated.