Not necessarily. The DOHC is by no means easy. SOHC->DOHC->Turbo DOHC (only because the turbo is in the way and the nuts/bolts won't come off easy)->H6. Have you tried replacing the thermostat yet? It is a cheap and easy fix if it is the problem. Get Subaru coolant and the Subaru cooling system conditioner no matter what you do.