Your Duratec has two O2 sensors on each bank. The first set is on the exhaust manifolds before the converters, the second is downstream in the exhaust. Bank 1 is against the firewall. It's not an easy job. Some people can replace from top after components are removed, others get it from below or I think, through the wheel well. A special socket is required. You may want to have an experienced mechanic do it.
Al
