How to: Custom login and forum?

Hey everybody!

I’m currently working on a new webpage which shall be become a community platform for several users. I’m using WP because of it’s simplicity.

I’d like the have a login box which integrates with the site’s design, also there should be a little “You are logged in as”-area once you are logged in. How can that be done? Is there a plugin or would I have to write something my own?

Secong there should also be a forum. I’m planning on using miniBB which is also very simple and has an integration-tutorial for WP. But which files would I have to integrated in order to use the sidebar or list_pages-function?

Thx in advance, Tim