You can do an advanced search on Ebay for completed auctions for the Shadow stormtrooper helmet to get an idea of what they are going for / have gone for. Whatever the number in the edition run will tell you how rare they are. If there were 500, then that's as many as were possibly made.
As for the Samaritan, I'm not sure what you're asking. You're wanting to know if it was "anything special"? Special is a relative term. Are you asking about what they might have used for the base gun? Are you wanting reference pics of it? You can do a search on this forum, as I know there have been all sorts of discussions about it, and maybe you can find the info you're looking for on one of those threads.