Hi,
I have to admit that i'm no programmer either and documentation on how to use an api in Subsonic isn't very clear.
Anyway, I found out that using the next line creates a new user on my Subsonic server.
http://MYDOMAIN.SUBSONIC.ORG/rest/createUser?u=ADMIN&p=PASSWORD_ADMIN&v=1.12.0&c=myap&username=NEW_USER&password=WELCOME_NEW_USER&email=joe@foobar.commydomain.subsonic.org= the web-adress to your subsonicserver.
u= name of someone with admin privileges.
p= adminpassword
username=name of new user
password=password of new user
email=email adress of new user.
Studying the different parameters which you can specify it seems to me that it should be possible to manage your users without too much difficulties.
Also there are some more api's to manage your users:
getUser getUsers createUser updateUser deleteUser changePasswordPerhaps some reading will help you some more:
http://www.subsonic.org/pages/api.jsp