First of all, this is in the wrong forum - hopefully it will get moved.
Second, there are people lined up on the Ford and Chevy sides pretty much just like Dems and Republicans. And like political views, if you subscribe to one side or the other you're not likely to be swayed to see the other side. That being said, it was not a mistake to buy the Chevy. The 454 is a tried-and-true power plant with out any critical flaws. Yes every engine design has its common quirks, but head gaskets aren't one of them on the 454.
$18k for a head gasket repair is obscene, even if it requires removing the engine. I would bet it can be changed through the doghouse. If so, it's a $1,000 job at most. About 1/4 of that if you do it yourself.