The round white screen filter is just pressed into the petcock casting.
You can remove it by inserting a thin screwdriver into the hole and
carefully catching the edge of the filter.
Filter should come out easily.
The fuel line on some models is very short, what I did was replace it with enough line to form a 'loop' about 100mm (4 in) in diameter with an inline filter in the middle. The loop allows you to raise the tank slightly, which makes removing and refitting the line much easier.
Norman