pilgarlick

Hi, Gents. I am trying to change the fuel filter on my 2002 2 litre diesel DCDI Mondeo, which looked as if it was going to be such an easy job. But.... I can't immediately see how the so-called quick release fittings work, and don't want to put too much force on them until I do. Do the plastic quick releases have to come all the way out, or do they only have to come out far enough to allow the fitting to come over the shoulder on the fuel pipe? Or do they come far enough out to "lock" into a position that will allow the pipe to be pulled off the filter stack? Will I damage them by levering with a screwdriver? I have pulled one out at least 3 or 4 mm, but I still can't lift the assembly off the filter pipe. Any advice would be much appreciated.