I may be looking into changing a few of mine this or
next week...
crawled under mine today, located them all..
if you have the correct tools, its not as bad as it looks
really. They make special O2 sensor wrenches and sockets
for harder then most sensors to get to.
Matco and Snapon both offer their share of "specialty
tools" .
The one on the pass side you can get to the plug from
the top, its not that bad, just follow the wire up and youll
find it.
A crows foot may work too on getting them loose too
just be sure not to round off that sides, that happens alot
if they are stuck in there from age.