How mechanically apt are you? I would just sell it as a running car with a bad head gasket before it bends a rod and quits running. Somebody might buy it for $1500 and fix that head gasket and get some more use out of it.
With the premium people are paying for a used car, I’d say if you can get the repair done affordably enough, fix it and keep it. Only when there’s a catastrophic failure is it worth replacing.