I wouldn't doubt that it's a little of both. Once I started going through coolant like mad, water was used. But the previous owner's history... not sure.
I've located all of the needed parts on subarugenuineparts.com (other than a timing belt). They beat all prices, even with shipping. So if you are like me, have a bad head gasket and need to redo a motor, I'd highly recommend them for your parts needs.