oxygen sensor after cc-1998

I have a 98 taco with 4wd and 2.7 and 5 sp mt. Autozone said I needed an oxygen sensor past the cc. I got one and its a Boch. It is different than the factory part as the boch has a 22 mm nut and a thicker flange.

Part number is 13104, and seems to match up on paper. The factory sensor does not have the 22 mm nut. Assuming Autozone gave me the right part, how do I get the factory part off. The two small nuts are badly corroded, and I do not know what size they are. If someone out there can help me with the nut size and any other info, it will be appreciated!