I am a total newbie to DNN so please pardon my lack of knowledge and possible dumbness of questions ...

I am basically looking for some guidance as to how to begin with integrating our eCommerce site with DNN.  My manager has asked me to work on the single-sign-on part of it to begin with and then integrating our user taxonomy with DNN taxonomy (topics of interests, and other user attributes).  I was hoping that there would be a DNN SDK that I would be able to somehow use to do this stuff, but even after going through tons of documentation, I haven't found anything useful that I can use to even begin working on it.  There are no code samples anywhere and no instructions.

We have an eCommerce site built using .NET 3.5 framework with SQL 2008 as the backend platform.  Currently, it is a standalone site with no CMS at all (just uses masterpages and CSS stylesheets).  I am looking to do the following:

1) When a user logs into our site, I want to log the user into DNN as well

2) When the logged-in user changes his/her profile and topics of interest, I want to update those in DNN as well

3) I want to be able to create new, custom DNN modules (functionality wrapped into .NET user controls) and place them into a DNN template for use on the website

I was hoping it to be simple enough, but apparently it is not.  Can someone help me with any direction on how to go about coding this, any code samples, or any documentation?

Thanks in advance.