Be careful when undoing the screws of the black box (pressure actuator). The whole system is under fuel pressure which will be released when you untighten them. There might be some petrol spray. Then remove the actuator but don't loose the two small green gaskets at the back of it.

Oh, and better use a good screw driver for the flat head screw on the back of the unit. It usually sits very tight and is made from weak metal.