Just changed out my oxygen sensor and I thought I'd make a searchable thread here in the DIY section. What a pain in the ass, my body hurts like hell from wrenching around in awkward positions under the damn car.
Anyway, some tips . . you'll wanna hit those threads with WD40 and let it sit for an hour or two. Even with that, you'll probably still need a breaker bar to get it to release. If you're searching around and can't figure out what size socket you need, it's a 7/8". But it's a special one you need; one that allows the wire to pass through the socket. BavAuto has them for $19, but forget that crap. Run over to your local Pep Boys, they have the same thing for 9 bucks. Here's a picture of it, with the o2 sensor sitting in the middle of it: