Populating an array with the usernames of a membergroup via SSI

[Father Time]

I would like to make a webpage that utilizes the SSI that can access my forum, locate a membergroup, populate an array list with the username of the specified membergroup, then use shuffle to mix that array up and then return the

• value from the array to do a random drawing from that membergroup. Anyone able to assist me with this?
  
  I don't know how to find a the members of a specific membergroup using SSI (or any other method). If I can get this step down I can do the rest of populating an array and doing the drawing.
  
  Any suggestions on where to start with such a project? I am comfortable with modifying and creating basic php, but my basic understanding of PHP hinders my understanding of database quiries within SMF (I can understand it when I read it, but Im not familuar enough with the software to know where to look).
  
  Thank you in advance to anyone who can make sense of my question and offer some assistance. Good evening!