I would am grateful for any detailed tips on how to replace this 0 2 sensor. Do components need to be removed to gain access? Removing the sensor itself looks doable, but could not see the plug-in end of the assembly.

Also, having replaced the front pre-cat O2 sensor and starting up engine, codes cleared, but engine still idles rough. original codes were:

P0131 O2 SENSOR
P0171 TOO LEAN BANK 1
P0172 TOO LEAN BANK 2
P0300 MISFIRE

a mazda mechanic mentioned something about, if i understood correctly, reseting the computer (or something like that) - - almost as if he was suggesting starting with 02 sensor replacement, but not sure that would take care of the problem.

thank you very much for your help.