I've used several lists/forums to consult on maintaining Subarus 1989-2015. The head gasket issue, bilaterally, was ubiquitous, along with loud valve clatter (unrelated, fortunately).

IME the head gasket failure rarely leads to cylinder/piston ring or wrist/connector/main bearing damage. Cylinder wear @ > 180k miles if the engine was well-maintained - even if that meant pouring more oil through it than a 2-stroke. Of course make sure the timing belts are replaced with the gaskets. The water pump should be replaced if substantial oil seeped into the coolant. A Subaru specialist mechanic will be familiar with all the details, they've revived a lot of gasket failures.

I love Subaru engines (in Subaru cars!), but didn't have the $ when Cunegonde needed a transplant. Went with a rebuilt 2.1l which is reliable and slightly less underpowered than the 83.5 1.9l. 

Best wishes in a quick & competent repair!