02 sensor dead, supect bad cat, need suggestions

Hello,

I have a 2002 Ep3. It just rolled 180K on the odometer.

I have had an P0420 code for about 6 months. It goes on an off at random, sometimes it stays on for a few weeks and its off for weeks other times it several days or hours.

On Saturday i was driving to town and was coming up to my stop when the car lost power, i was doing about 3K RPM's and it was like I had lost fuel. If i pushed the pedal all the way to the floor I had power again. its was most noticeable in 2nd gear at the 2-3K RPM range.

I m in idaho and there is tons of snow so i added some HEET to my fuel just to make sure i didnt have water in the lines. CEL went away.

After the car sat for 30 min while I ran errands i was able to drive it home without issue.

I have been commuting back and forth to work every day and its been behaving fine.

Today that changed. On my way home about 5 in from home I lost power again. CEL had come on about half way home. I was able to make it home and was able to pull codes with my ODB2 reader.

I am still seeing the P0420, but I have added a P0134 and P1157 that i did not previously have. I checked my voltages for my 02 sensor and i was showing voltages on both. The car sat a couple hours while I did some research. I went back out and started it back up and watched the live stats and the Bank 1 02 sensor is dead. 0V.

I know i need to replace the primary 02 sensor at this point. However, did the bad cat code indicate the cat is plugged and that caused the sensor to fail due to my negligence in now taking care of the cat sooner? I was under the impression that the P0420 just indicated the cat was operating less than normal efficiency and that since we don't smog that i didn't need to worry about it. I was going to do the spark arrest or spacers on the secondary 02 to get the code to go away, but it hadn't been high on the priority list.

sorry for the long leadup. I guess the main question is, what the best steps going forward Replace the cat with a Random tech unit and pop in a new primary o2? I am not really a gearhead, my ep3 is bone stock. I don't know if the cat is bad or just the o2 is bad. I don't want to waste a bunch of money. I was considering selling the car, but I wont sell a car that isn't working properly or has been jerry rigged to temporarily work. Suggestions appreciated.