PhP, MySql Programmer New to Asterisk Question

I have a dedicated Linux ( Fedora ) server and I would like to install Asterisk and run it for this purpose:

My website subscribers call, put in their userid and record a message. After that - the message is playable via their profile.

How difficult would this be to set it up and can someone tell me what steps this would involve?

Thank you

Get asterisk up and running and get a couple of extensions running to either hard phones or soft phones. Once it works and you are a little more familier with it check out the wiki for information on the Manager API. With the manager API you should be able to do what you are looking for. (specifically look for OriginateCall)