I'm going to change the front oxygen sensor in my 2000 Outback manual transmission. Do I just need an open ended wrench? Is it much easier with any other tools?

Some PB blaster is another good tool. Let it sit for a hour or so. That should help.

22mm or optionally 7/8" 6pt wrench is your friend on this job. On '00obw though, connector might not fit through the wrench, in which case 22mm or 7/8" flare nut wrench would be helpful.

A close quarters O2 sensor tool is a big help. Available at the parts store.

Running the engine for about a minute will aid in loosening the sensor. Plus if you are in canada you can warm your hands on the pipes.

I had a proper sensor socket and full set of combination wrenches, and the best tool on my 99 was a box end with a sawed off (shortened) handle. I believe it was a 22 MM.