read a few posts up, they can be had cheaper - im not sure why i keep replying to this thread though.
if you have seen these cores and how they are setup, there is no fixing them
NATRAD radiator shop
$275 - alloy core
$345 - copper core
NISSAN
$365 5 years ago
the info is there, by all means try to get it fixed, but it would cost more than just getting another core.
for the cost of 3 tanks of fuel - you get your heater back in the middle of winter. up to you i guess