DIY Downstream O2 Sensor Replacement?

After noticing a rattling noise upon starting and acceleration, I crawled below to figure out what the problem was. The downstream O2 sensor was having issues. I immediately noticed the rubber gasket is completely rotted. And there doesn't seem to be a bolt on one side holding the whole assembly in place. I can move the entire sensor and the metal shield which causes the exhaust to make a strange sound. (Obviously I did this only once and won't be driving it except perhaps to the shop) Ideally, I would like to fix it myself, is this doable? I am mainly worried about access since the metal shield is keeping me from accessing it with any tool.

There is a good picture of the metal shield on this thread:

https://www.tacomaworld.com/threads/rear-o2-sensor-shield-replacement.502439/

 

not sure how mechanically inclined you are, but the shield/o2 sensor just bolt on. You can get a bolt from a hardware store and gasket from toyota. Should be a fairly easy fix.

 

Will try it. Do you have any tips on how to actually get in there? It feels like there aren't any bolts on the threads at all...

 

https://www.tacomaworld.com/threads/rear-o2-sensor-done.142451/