617 Head Corrosion

[GRIESL]

Ok, I love my car, so I treated her to the very best--reman head from Metric. Sent my head in for core credit and here's what I received in return. Caps lock is their doing, not mine--sorry....

HEAD CORE NOT REPAIRABLE:: HAS SUFFERED EXTREME LONGTERM EXPOSURE TO WATER
CONTAMINATION. COMBUSTION CHAMBERS ARE CORRODED OUR IN NEARLY EVERY CYLINDER
(CAUSE FOR CONCERN REGARDING YOUR CYLINDERS/PISTONS WHICH ARE ALSO EXPOSED
TO THIS CORROSIVE ACTION??)

First, I'm bummed that I'm not getting my $400 core charge back - especially after paying $80 to have it shipped there, but second, is this a large cause for concern? I've owned the car for about 10 months and put 6k on it before doing the head, so I assume whatever was done to cause this was done by previous owners? The block, pistons, cylinder walls all "looked" ok, but honestly I wouldn't have known what to look for. Car runs real well and a whole lot better with new head. And if I'm ok now, should I go out and get a water separator fuel filter? Confused.... Any thoughts?

PS: Heard of another dude not getting core charge back from Metric. Any reason to be suspicious?