I hate modern cars...

Check craigslist. I got a new radiator for our 02 minivan from a nearby place in Sacramento that sells high-volume and cheap from a warehouse. East European or Mid-Eastern guys, but polite and know their stuff. Of course they prefer cash. Surely you have the same places in the OC. Bought another new one cheap on ebay (96 minivan), but apparently a factory reject since the side tanks weren't parallel, so could only attach 3 of 4 bolts, but works and isn't going anywhere.

Re heater cores, I was pleasantly surprised to find that in my Mopar minivans, it slides out sideways near the accel pedal. All you need is to disconnect the steering column at the floor (easy) to make room. Some newer cars are nightmares and the designers should be flogged. I have heard of having to remove the whole dash. My 80's Mercedes' is a 2-day job of tearing apart the entire center console and new heater cores cost $500 if you can find one.