P0420 Woes: Replace Converter "Back?" on a 2005 @ 192k

Hey gang!

OK - I've been reading the related P0420 threads and they've been super helpful but I'm still a little unclear on exactly what my next move should be when it comes to getting a few more years (hopefully!) out of my beloved 2gen.

Backstory:

Replaced the muffler on this thing a few years back. No real issues otherwise to speak of. Well, that heat shield over the muffler fell off two years ago and I was advised that replacing it wasn't really necessary (!!!). I typically wait about 4k miles to change the oil and - yes - I am *now* aware that 2gen tend to burn oil quickly (thanks for hammering that home for me!).

Suddenly, exhaust sounds pretty awful...like a muscle car. I got on the ground and checked it out while the ICE was running and, sure enough, there is exhaust coming from the back *and* front of the muffler. Pipe that runs under the center of the car doesn't sound super great, either.

In hopes that I could make it another five days before I am able to drop it at my local shop, which has always done fantastic work for me, I keep driving it. Until yesterday, that is. CEL is now on. Panic ensues.

I'm out of town for work so I find a Toyota dealership as soon as I arrive at my destination, take it in, and they tell me I need like $5,000 in repairs. OOF. The very kind guy at the counter, who was also not-to-subtly recommending that I lease a new Prius (lol), says that I need to "replace converter back and O2 sensors".

I kind of figured the exhaust situation probably triggered a sensor and I suspected that, at worse, the cat needed to be replaced. However, the way the guy explained it to me, it sounded like they wanted to try to "rebuild" the back of the cat and keep the front?

And now the questions (finally, sorry):

1. Is he referring to the fact that there are 2 types of catalytic converters in the 2gen Prius? (correct me if I'm wrong or confused...)

2. I know I should expect put some $$$ into a car this age and mileage - but in Ohio, I don't think I need an OEM cat so would YOU (yourself) just sink a few hundred bucks into an aftermarket cat like the Magnaflow I see referenced so often, new sensors, clear the code, adjust my oil change intervals, and just try to ride it out another year or so?

3. Dude also recommended that I have my water pump and "belt" replaced. I asked which belt. He said timing. I think he meant serpentine. The water pump was replaced as part of a recall several years ago and, compared to the cat/sensor repair/replacement, it's a relative drop in the bucket but is that something you've encountered, too?

The guys who actually DO the work were still hanging out by my sweet old girl when I walked out to drive away...loudly...and they actually leveled with me: just take it to a muffler shop and have them patch you up at this point. No sense in putting $5k into this thing - that's a down payment on a newer model.

I love, love, love my 2005 and - yes, both financial concerns and sentimental (perhaps irrationally sentimental) attachment may be influencing my decision-making.

So, long story short (too late): is an aftermarket cat worth it and can pretty much any muffler shop or (preferably) my usual shop do this repair to keep me in this sweet thing for another year or two (or 100,000 miles)?

I can scan and share the quote from the service desk with the details of their recommended "immediate repairs" if it helps inform anyone who made it this far in the post...

Thanks everyone and sorry if this is a super-duplicate post. Always appreciate the wisdom and insight here at PC!

kate