Showing Most Recent members (with pics) and recent posts

I gather this a completly newbie question, so apologies in advance.

I have installed WPMU along with the edu-clean theme and the sitewide avatars. So far so good. It's looking great!

I want to add two sections to the home page:

1. A list of X most recent members, which includes their name and profile pic (avatar) at a minimum
2. A list of Y most recent blog posts, which includes the member picture and name and like a 2 line extract of the blog entry which hyperlinks to the blog.

I got confused since I see there is a RSS feed apparantly built into WPMU (thats how much of newbie I am) but I have no idea how to activate that or even if that is the right way to go. Or should I be using a plug-in.

I don't mind editing the theme PHP files, I just dont now where to get the info for 1. and 2. above from.

Thanks for pointing me in the right direction,