Sadly I don't have a manual for the Estate 400 (only that low-res picture), but can help with pictures of some of the parts, including the trigger & cable, I have a few little trimmer head parts but none of the bigger pieces of the trimmer head.
The stop/kill switch on most of the these engines has always been a simple shorting switch, either the brass strip type or a bought in switch, some of the chainsaws have a more complicated switch mechanism in the handle.
David