You will need to get an "Oxygen Sensor Socket" which fits every one I've run across - it's a really deep socket with a relief cut to pass the harness connexion (you could probably use a wrench as well, if you have the room.)
I find that working while it's still farily hot helps, as that loosens things up a bit.
When you put the new one in, MAKE SURE it has never-seez on the threads - most do from the factory, but put some on if it isn't there already!
2.46L Carburetted sounds pretty early, so you should only have the one in the manifold. If you want to be sure, slip under and look between the catalytic converter and the muffler for the other - that's where it would be ($5 sez you don't find one, so how will I collect?)
5-90