2nd Gen Tacoma upstream O2 sensor replacement

Hey there hive mind.

At 210,000K I was thinking of spinning a couple new up stream Denso O2 sensors into my '06. Had a look at it and it seems like a bit of a bitch to get in there. Any tips and tricks to getting up there to spin them out? Additionally neither Napa or Lordco seem to have a Denso number for the upstream sensor and they are only offering me Bosch sensors, is it because they are not available or because I'm in Canada?

 

Are they throwing a code? If not, I'd say don't worry about it. I've got over 482km, 300k miles, on mine.

 

If they were causing a problem they would be coding.

if you're wondering about fuel mileage or the performance of the EFI system get a little code reader that can let you watch short/long term fuel trims

 

No codes at this point but it often but not always has a low guttural growl when releasing the last bit of the clutch that sounds to my ear to be spark knock. I had a '90SR5 3.0 that never threw a code but I replaced the O2 sensor and it brightened right up the way the engine ran and stopped the uphill pinging.

 

I have a 1997 4x4 tacoma with a 2.7L engine and I'm wondering how hard would it be to replace the O2 sensors ?