P0301 misfire, dealer says blown head gasket - options?

I've read thousands of posts on these forums over the years as we've had two Priuses, and have gained so much valuable info, but I guess this is my first post!

A bit of recent history before my current situation will make sense:
Around six weeks ago our 2013 Prius V had CEL P0301, cylinder 1 misfire, and occasionally had brief but serious knocking sounds on cold start-up. I read posts here for hours, watched YouTube videos (thanks Nutz About Bolts!) and dug in. I changed the spark plugs, noticed number 1 was a little oily and dirty but the electrode tip was clean, the others were dry and normal. I poked a light in the spark plug holes, all pistons had a similar thin layer of carbon. I labeled the ingition coils and reinstalled them in reverse order. I cleaned the intake which had almost 1/2" of oil at the base and the EGR ports were a bit clogged. I cleaned the EGR cooler, pipe, valve etc - soaked overnight in a warm solution of PBW (powdered brewery cleaner) and sprayed with a strong hose nozzle, got it all shiny inside without a pressure washer or repeated soaking! The cooler wasn't blocked but had lots of buildup. I cleaned the injectors which seemed super clean already. I replaced the PCV valve and installed an oil catch can. In the process, I drained and refilled the coolant. It took me a week of focused time, around half of which was gathering info here, and cost only $330 in parts and tools. It ran smooth and strong after that, no knocking, and the codes cleared themselves after a few days of driving.

The above paragraph should be its own whole post with lots of photos that I took, but after working on the car I was behind on everything else, and it got out of sight, out of mind. Until last week, when I noticed it knocking some in the same way it had earlier, and after a day the CEL came on. I had it read, and same thing - P0301. I had also tracked the coolant level in the reservoir carefully in the six weeks and ~4000 miles we've driven it since I did the work, and it has dropped a bit - I put it right at the F line which is just above the seam, and after a few weeks it was at the seam, and last week when it started knocking I noticed it just below the seam. This is all consistent with the misfire being caused by a head gasket failure instead of bad coils, dirty injectors, clogged EGR etc - all the stuff I was chasing down the first time the CEL came on.

I don't have tools to diagnose a failed head gasket, so I called around and everyone had a 1-2 week wait except the dealer. They said there's hydrocarbons in the coolant, which in context of the misfire indicates a blown head gasket. I think they're right, since I changed the coolant less than 4k miles ago so hydrocarbons in new coolant is a strong signal. But I thought they'd do a compression test or leak-down test to double check instead of just testing the coolant.

They said they don't recommend replacing head gaskets on Priuses since the aluminum head can warp, so instead they replace engines, and quoted me $7,800 to swap the engine for one from GNR with 90k miles on it and a 1 year warranty. I'm not inclined to do that, mostly because we paid $13k for this car in January 2021 when it had around 90k miles, it has 130k miles now, and I could easily find an OK car for $7,800 and just let this one go. But that feels bad also, mostly because it's the perfect car for our needs, and partly because I put new tires on it just before the first CEL came on, have a set of winter tires for it, and just last year had to do the brake booster repair out of pocket since it was just outside of the TSB extended coverage. At 11 years old and 130k miles, it feels like it shouldn't be nearly totalled by a blown head gasket, and shouldn't be sent to a junkyard. It seems like the right choice is for me to do the head gasket job myself, but I'm hesitant about that - I did it once on a Subaru at a pro auto shop where a friend worked and held a bay open for me, around 20 years ago. Now I'm middle aged and busy, have a garage and can figure it out and get tools if I don't already have them, but it seems like a huge and risky job on the car my wife and I share as our daily driver.

I'll be calling independent shops tomorrow to see what they would recommend and get some ballpark pricing, they may have a palatable option. But I want to know what you all think - should I trust the dealer's diagnosis or get a compression or leak-down test? Does it make sense that the dealer doesn't replace head gaskets and replaces whole motors instead? I don't remember seeing people say that here. What have you paid to have a shop replace the head gasket or swap a motor? How big or hard or risky is it to replace a head gasket in my clean, dry, well-lit garage, given I have a fair bit of amateur mechanic experience and am good at figuring it out? Is there anything I'm not thinking about here?

The car is paid off and we can get a loan to replace it if necessary, we have an older second car we can use in the meantime, and my MIL lives across the street and we can often borrow her car. So this isn't a desperate emergency, but we can't drop $7,800 on a car that's worth around 10k, and trying to sell it and buy something else would be a similar hit, assuming we go for another Prius V since it's the perfect size/capability/efficiency for us. I feel like I have no good options, but I have time and resources, and I hope you have ideas!