Need some help with custom post types and dashboard widgets

I’m doing a project for work that includes some plugins that are a little beyond my normal comfort level — it’s not something I couldn’t do, but I feel ridiculous looking up some of this stuff at work that I’m not sure about, so I think it’s time to ask for some help. I have to make a bunch of costom post types with custom meta boxes… I get this in concept but I’m not confident with my code… my real issue is the dashboard widget to update the meta on a certain post type — the client needs to be able to make a selection (of posts of 2 other post types) from the dashboard and the post they select will get a reference (post id number) in a hidden meta box. I’m not sure how to do this and I’d be immensely greatful for some guidance. Thanks!