I just replaced my Shadow 2 hammer for a competition one last week. The strut and disco pins are staked into place and you need a taper pin punch (could try a regular pin punch but risk breaking it) and a hammer to give it a few solid wacks to pop them free. Use a good block to support the assembly like a hockey puck with a small hole drilled in it to allow you to drift the pin.
I lightly polished the sear edges with a stone 'cause it felt very very lightly gritty.
That said, I've read of a couple instances where it wasn't a drop-in fit but for the majority, it seems like it was.