There's a few screws - the mudflap has to come out, then there are screws holding the plastic against the edge of the guard, and a couple of those plastic clips further in.
Remove the mudflap first, then work your way up. The plastic just pulls forward revealing the pump which sits at the bottom of the bottle and just pushes in with a silicone tubular seal to prevent leaks. One electrical plug and the output hose and the pump is out.