How to setup referrals for membership?

I have my aMember signup page ready - I want to offer member a referral discount though. For example, if the reffer a friend, they would get 1 month free.

A couple questions for aMember gurus:

(1) How can I add a "reffered by" custom field to the signup page so new users can enter who they were reffered by?

(2) Can I have a refferal link for members? For example, if they went to signup.php?refferal=john, when they signup "john" would be automatically eneterd as their refferal person

(3) How can I add a month of free service to an established paying account?

Thanks

Me, too!

I am also interested in this plugin. I checked out the list of plugins on webpage http://www.cgi-central.net/scripts/amember/features.php#protect but I wasn't able to recognize one.

Does this plugin have a name?

Sincerely,
R Lorenzen

does the refer work with points as well? I mean can you costumize it using points instead of weeks added to the membership?

I'm very interested in that too. How does it work exactly?