hv battery repair

I have a 2005 prius with a little over 200K on it. Was running fine (no lights or problems) last fall until my 16 year old son decided to take it joy riding and swipe it into my neighbors fence. It ruined the drivers side front fender and front door, and totally smashed the coolant thermos. I had it loaded on a wrecker and brought home - it started and i drove it up on some ramps - but then got busy and did not get around to repairing it til now (9 months later). I bought a used coolant thermos of ebay, refilled and bled the coolant system - hooked the 12v battery back up but it won't start.

I invested in a $30 reader from amazon that came with "special" version of techstream that i eventually got working with my win10 vm on my macbook. Alas, it says i have code c1259 and c1310 and zooming in further to see the battery health, it shows blocks one and two are only 3+volts while all the others were like 12.61v. Before I take the HV pack out - i wanted to get opinions. I have $100 into it now with the coolant thermos - looking at probably another $500 for the fender and door - i really don't want to put a lot into it given how many miles it already has - although it would be nice for my son to drive it instead of my old 1986 ford f250 from a gas perspective. (The f250 fwiw is alot easier to work on!)

Have people had luck just replacing the individual cells - I also see that some people recommend using the gen3 cells because they are newer. The cars first pack died at 110K and this pack from a junk yard had I think 60K when i paid a guy $800 to put it back in 2012 or so (so it have around 150K on it). Putting $600 for the body work plus another $800+ for a used battery seems like a lot to spend on a car that is mostly used up but i could see spending a few hundred on cells or a couple of new blocks to get maybe 10-20K more miles at which time the kids will be out of school and needing to get something of their own.

Thoughts?