before replacing the head gasket, let the mechanic first check the oil cooler. this is common to isuzu engines ng hilander, there might be tiny holes in the oil cooler which is usually rusted na if you have not been changing the coolant often.

the only way the head gasket will get busted if the engine before had been overheated. Isuzu engines are robust but its no.1 enemy is overheating.

BTW mahal yan oil cooler na yan mga 4k sa casa, some technicians sa casa just weld the holes if its just small pa lang sort of band aid solution. when changing the coolant, be sure to flush the entire cooling system to get rid of oil deposits in the cooling system. I know this for a fact since it happened to my inlaws hilander also.