Cat replacement for 2.0L petrol Si4

[LRD414]

My 2013 2.0L petrol has a persistent cat fault (P0420). Looking at replacement options and not finding much “how to” online. Any experiences or tips with this job for the 2.0L petrol?

[LRD414]

Used the Gap iiD to check live values; logged o2 sensor 2 on a 3 minute drive after engine warmed up. Peaked at ~0.82v and down to 0.1v. Generally the high value was 0.77 to 0.79. Showed a regular sinewave style pattern but stayed down at low value a couple of times i was waiting at a stop sign. Held at higher range (0.82 - 0.78v) with open throttle up a hill.

Not sure if this is indicative of a normal o2 sensor. Couldn't find a sensor 1 voltage in live values list, would have liked to compare the two sensors

Also logged fuel trims on a short run. Short Term Fuel Trim of -15% to +15% but mostly -10 to +10 over a short drive. Long Term Fuel Trim drop from zero to -5% over same short drive.

In the absence of weird figures I’m assuming it’s the cat rather than sensors. The flange bolts closest to engine look hard to get at, close to drive shaft and transmission