Gordon -- This sounds like bad news. If the hose connections don't feel damp, I can't think of what else it could be besides the core. Do you have the time and a heated garage available? With all the parts in place beforehand, you could easily do this in a relaxed weekend. Rather than take shortcuts, if the core's starting to leak, I'd be suspicious of the other components -- fan motor, hoses, thermostat -- they should be at the end if their service lives and probably need to be replaced as well. Since everything will be apart, those replacements would be far easier.

For better or worse, you identified one of the quick pre-purchase checks of a 240 -- turn on the defroster with the windows closed and see if they fog and if you smell sweet fragrances.

Rob