I went for my emissions test and it failed. The engine light was on, so they did a diagnostic and it said that I need to replace the oxygen sensor & the DPFE. I called a couple of places & they said it would be $600, I called another and they said $300. I don't know who to believe. I'm a pretty good with mechanical things. Can I change any of these sensors myself or is it too complicated for someone who's not a mechanic? I'll do it myself if I can save some money. My car is a 2001 Ford Focus ZX3.

Its so simple to replace the o2 sensors, You have 2 on your car both running $50 bucks, If you buy it from a parts store you can rent the o2 sensor removal tool. All that tool is a socket with a cut down one side..and to remove the o2 sensor. You disconnect the negative battery cable - then you locate the o2 sensor - then unplug it - put the socket on the sensor - attach a ratchet - take the sensor out

Installation is reverse exept you should but some anti-seize on the threads of the o2 sensor - thread it in - tighten - plug the wire back up - and your done.

You have two sensors one located before exhast manifold and one after.

Hope this helps

Please post the diagnostic code that you got from the shop.

I can help you if you get the code for me!