The dome is not likely to leak unless the jam nut for the adjusting screw is loose. Check your hose connections. The other leak source could be the PA valve. That is the valve body the two hoses hook to. There are O-Rings on the base of the valve that sometimes leak. Get a can of Brake-Kleen and clean up the area around the PA valve and see if you can spot where the oil is coming from. Note that the PA valve is adjustable and if it is not placed in exactly the same spot, the car will self steer to the right or left. Read the FSM about adjusting the valve. If you need to remove it to replace the O-Rings, purchase the high density O-Rings as the cheap auto parts variety are too soft and will fail quickly. The dome does not have a user serviceable gasket, the gear would have to be rebuilt.
Dave