I know it sucks but there is no other manufacturer that will cover stuff like this outside of normal warranty. I had a 83 Chevy Z-28, bought new, took it in twice for transmission problems, R5 I think was the model no.. It only had a 12 mos. or 12,000 mile wty. Sychros just kept failing. The last time I took it in I had about 11,000 miles. Told the service man I had to drive it home and back, 3000 miles roundtrip with the bad 1st and 2nd gear sychros and he said no problem, well fix it when you get back.
I fought Chevy for months and finally got my money after exceeding the warranty and failing for the 3rd time/4th time. Although it had been repaired twice and reported prior to my trip home.
Traded it in for a 1977 International Scout II. Haven't bought a Chevrolet/GM product since and never will. I'll buy a Yugo or Wego before I'll ever buy a Chevy. Have they lost alot from me. Maybe, I've purchased 5 new vehicles since then, if I had been treated right at that time they probably would have been GM. My money has went to Ford and VW. Just a little history.
I don't think doing it yourself would be terribly hard. I've changed radiators on many vehicles, I know they didn't have all of the coolers and such but if I recall correctly this thing comes out as a package, split it replace the unit, and reinstall. I'm thinking cost of radiator plus fluid? Just a thought for DIY.