from idea to product, workflow question

Folks, if you don't have patience, quit reading right here, this is going to be long. ;)

Setting:
Windows 2008 R2, .Net installed, IIS installed, ASP.Net installed
I am admin on that box, I can do whatever I like to it. Server is part of an AD, I am not an AD admin, but I can create groups for my OU within AD and add/remove users from it.
I also have VS 2010 (thanks MSDN AA!), and I took some C++ classes way back when. I know about data types, I know what a class is, and then it sort of fizzles a bit when it comes to knowledge. I do have Murrach's books on C#, ASP.Net, and MS SQL.

Goal:
What I would like to create is the following functionality;
User accesses a secure web site which asks the user to log in with AD credentials.
If user is authenticated then user will receive a screen that allows user to enter an email address and send that info to the local server (same server that runs the web site).
The server then creates a local (non-AD) account for that email address, adds that user account to an existing group, creates a user directory, adds that account to the FTP server and sets all permissions necessary for that user to access the server via FTP.

Upon completion of those tasks both the user who requested the account creation as well as the user who's account was created will receive a notification by email that the account was created. The user for whom the account was created will be directed to a secure web page where he or she can then set a password for the account. Once the password is picked the user account is updated accordingly.

The created user account is temporary and after X days (where X is determined by the administrator) the all data for that account will be removed from the system and the account will be deleted. The user will be notified 5 days prior to deletion and 1 day prior to deletion by email.

That's the basic concept, it can obviously be infinitely extended with reports, additional features, etc., but that would be the basic functionality.

Now the issue is that I have no idea where to start, I have no real idea on what is required to make this all work. The way I would break this down in rough pseudo code is:

1. User authentication against AD via a web interface. (ASP?)
2. User creation, directory creation, permission settings. (ASP? C#? PowerShell?)
3. Email notification or account creation and pending account deletion. (???)
4. Daily check on expiring accounts (???)
5. Deletion of expired accounts, removal from groups, removal of files/directories (???)

I know I need to take this one step at a time, modular basically, make the user authentication work first, test it, once it is done move on to the next step. Still, my question is where do I go to find out what's required to actually make all of this work?

Thanks in advance for your time and consideration!