How do you replace a head gasket on Volvo 940?

To replace the head gasket on a Volvo 940, first disconnect the battery and drain the coolant. Remove the intake and exhaust manifolds, as well as any components obstructing access to the cylinder head. Once the head is free, carefully lift it off, replace the old gasket with a new one, and reassemble everything in the reverse order, ensuring all bolts are torqued to the manufacturer's specifications. Finally, refill the coolant and check for leaks before starting the engine.