Need a members only section of the Blog

Hi all

I have been asked to do a site for an NPO, so they want it cheap and easy to use.

Basically their current site has half a dozen pages (that anyone can view) with info on them and they update it using frontpage.

What they want to do is add a members only section, with stories people can comment on and discuss as well as having some other pages everyone can view, I thought that I should be able to put the whole site into wordpress, but I don’t know how

I have looked around for this functionality on wordpress but the only thing i can find is

http://wordpress.org/extend/plugins/user-access-manager/

Which looks to do what I want, but will only work for an older version, anyone know of a version or something similar that works on the current version of wordpress

Any help would be appreciated