It's rarely the actual gasket that leaks, but the O rings on the plastic valve. They turn to brittle plastic with age/heat and allow pressured oil to get past the paper gasket.
Assuming the long 10mm bolts undo, it's a really easy job. I smear the paper gasket with LM grease, stick it to the housing and then fit it with a couple of bolts. Use a torque wrench to nip the bolts up correctly.