Any tips for replacing ML320 O2 sensors
 

If anyone has done this job I'd appreciate any DIY tips.

I've located the 4 sensors (the pre-CAT ones appear harder to change) and found replacement parts.

I'm guessing the old ones will be difficult to remove since they have never been replaced (1998 model). Not sure whether to use anti-seize on the new ones. Is there a torque setting for the replacements?

I'm hoping this will take care of the recurring Check Engine light codes 170 and 173. Already tried the MAF.

Thanks for any advice!

It is pretty straight forward. If I remember correctly there was one that was a bit tough to get to.
I just tightened them. Not sure about the torque.