Here is a thread about sexing them.
Sexing harlequin shrimp?
Most people seem to feed chocolate chip stars but I think that is just because they are inexpensive rather than the "favorite" food. They seem to eat them well anyway.
I have always heard that they exc;isively eat starfish so my guess is that the shrimp woud be ok, but wait till someone with experience verifies before you take my word on that one.
Hope that helps.
Oh and Woodstock has them so you might want to check out her chronicle. I know she has some great pics in there.