I guess first things first and apologies if this has been asked and answered already in this thread. Do you have any prior development skills at all?
If so then it should be relatively easy to adapt those skills to the .net environment/ syntax.
I terms of where to start it depends on how you learn best. If you are visual person then the online training sites will be a good place to start if you have access to them such as Lynda, Plural Sight etc.
If you prefer books then there are hundreds to choose from it is just picking up one that is suitable for you and the way you learn.
From the looks of it this is a fairly meaty project and although challenging may be a bit over ambitious as a starting project (if coming from ground zero) but could be built in phases to help aid with learning and focus on specific areas of the project.
If you are completely new to the .net world then MVC is probably the route to go rather than webforms (purely down to this now getting more traction and also helps re-enforce design principles)
I have this book which has helped me a lot with the conversion from webforms to MVC but also works with no real prior knowledge
http://www.amazon.co.uk/Pro-ASP-NET...=sr_1_1?s=books&ie=UTF8&qid=1363724287&sr=1-1
As I said you can't go wrong with one of the dummies books or something like this:
http://www.amazon.co.uk/Head-First-...=sr_1_2?s=books&ie=UTF8&qid=1363724367&sr=1-2
Also to help with getting a good user interface built using something like twitter's bootstrap will aid in faster development for a front end perspective as it takes out all the hassle of the complexities of html and css.
A good mocking tool for using bootstrap is
http://jetstrap.com This helps you craft a front end for prototyping in a very simple user interface and then allows you to play with ideas on the look and feel etc and when you are happy with the look you can then download the html and plug in the actual code side of things.
If you are looking to develop a cms (content management system) for your knowledge base then it may be worth looking at technologies such as umbraco and joomla.
But these maybe a step too far at this early stage for you.