Hello!

I have a web site (www.winner.gr) and I'd like to add a login system where the customer will be able to enter their username. and password. after they have subscribed for free. also in the login part I'd like to place a link that will send to the user his/her password in case they have lost or forgot it,like it is in yahoo for example.
What do I need for this, do I need a database or something and how can I connect all this functions together?
How much time will it take?

Thank you so much!