Upstream o2 sensor
 

What size is the socket do I need for upstream o2

I would recommend getting one of these: https://www.google.com/shopping/prod...ed=0CGYQ8wIwAA
its designed for it and has a cut out for the sensor wire. I believe the size is standardized at 22mm. I have not come across one my socket didn't work on.

Yes get one of those or the crows foot o2 sensor wrench, I have had to use it several times and has come in handy. I bought it at pepboys.

x2 crows foot 22mm should be ~$10

7/8s will fit.

You can use a 22mm wrench if you can get it on.