Hi Linda - with the volume of requests I get, I just don't have the time to get into specifics of this magnitude anymore - that's what I set up the rocketgeek.com support site for.
There would be a few possible approaches with varying degrees of complexity to adding a birthday field. You could add a single field, but you would need to be adept at writing some validation code using the plugin's filter/action hooks to validate that you are getting data in the form you want it (such as dd/mm/yyyy). Alternatively, you could use drop downs for month, day, year but you'd still want to use the form filter hook to filter the form layout and get them to display next to each other.
On the question of the sidebar, the plugin blocks the contents of the WP variable $content (which is the content of the post/page). The sidebar is something else altogether. The process of blocking items from view would be similar to how I have described it for displaying menus based on login status in this post: http://rocketgeek.com/tips-and-tricks/creating-menus-based-on-login-status/ (this is a free post on rocketgeek.com that gives you some idea of the tutorials and code samples available). It would be a little more advanced in that you would probably want to show some widgets if the user is not logged in (such as the widget to login). You can also use the logged in/out shortcodes in sidebar widgets, but that doesn't block all the widgets all together, that's more for working within a text widget.
On the last question, while there is the ability to display user data using the "field" parameter of the [wp-members] shortcode (described in the user guide here: http://rocketgeek.com/plugins/wp-members/users-guide/shortcodes/field-shortcodes/), that doesn't function as to display a list of users. This is some functionality that is actually on the project list for a future release and as currently planned, will come in the form of a shortcode. (At present, that is in the 2.9 feature release - the 2.8 version in development is an overhaul of the admin panel.)