Hi guys i want to change my fuel filter on a 2000 e220cdi.the filter housing has 3 pipes coming out of the top,2 are held in with compressed clips and the middle one seems to have a plastic prong clip which you pull out.the top of the housing is round with a serated edge,does this just unscrew anti clockwise fully or just by 90 degrees,would appreciate any advice as i like to do these sort of tasks myself,thanks fellas