SMF database integration with our own webpages

I am using a brand new installation of SMF 1.1.2
I want to use it's database for registration and authentication, but not use any of the forum webpages until they are SPECIFICALLY asked for by the user. In other words, I need you to create a couple of php functions that I can call from my webpages that will handle registration and authentication by using the SMF database.

A rundown of what's needed:

1. Create a registration page/function that takes user input and verifies it against the SMF database, before inserting the data into the SMF database
2. Create a login function that checks if a user's provided username/password is correct in the SMF database, and creates a session state if this is true.
3. Create an authentication function that checks the session state to verify if the user has logged in this session, and is true returns the username else returns "guest".
4. Remove the logout link from forums pages

A bit more info available here: http://fooooty.com

Quotes for the work please! No screaming rush to get this done, but I can't start porting other code into my game until I can get an authenticated session state going, and use the SMF database for it.

I'm using SMF for authentication as the forum will be a link available to users to chat, but will not be the main reason to visit the site. Many users will not use the forum, and so I want them never to see a forum page. In my experience, if you enter the wrong password, you see a forum error page. If I were to use the redirect-after-login function of the SSI.php, about one time in 100 I see the forum index, not my own. When you have thousands of users this may get a few grumbles, so I want the users never to see the forum pages unless the specifically click the "forum" link from my game.