Engine lost a lot of power P0123 code?

So about three weeks ago I noticed that my car has lost a lot of power. And it is also guzzling a lot of gas way more than normal. Ten one of the readers on the car dash, popped up, tsp sensor fault. Then, it's disappeared. So when I got home, I googled What could cause that warning light because I figured there was really nothing wrong since it disappeared. That was a big mistake. Because it told me so many different things that could be wrong and throw that. So I asked around if any of my friends had an o b d scanner, one did, but he didn't really let me look at it. He just was real quick. Boom boom boom, and I seen the code pop up. That said p0123. I believe. So I looked that up and it said, high voltage oxygen sensor. So I looked that up and that led me to the upstream oxygen sensor needing to be replaced. Is this correct?