Can you help a non-profit group? simple user Login, Approval and Profile

Hi there could any of you code experts please help me? Im a beginner in coding, more of a graphics designer. The site is:

I am looking for simple a script that will allow users of the site to:

a) Request to join (via email or the request is build into the script somehow)
b) The moderators have the ability to approve the user or not.
c) When accepted by a moderator, the user can simply Login, Edit their profile (nothing complex, just name, address, contact and job).
d) ability for moderators to contact members by sending an email to them.

There already is a forum that will allow users to communicate. I just need a separate, secure way of saving the user’s details, and to manage the user registering process.

Thats it!

The site is hosted in a server that has PHP4 and MySQL.

Any ideas are very welcome, as I dont have a lotta time to work on this, a ready-made script would suit me…

Many thanks!