As a matter of fact, Sitefinity CMS is a very user friendly application. People with really insignificant ASP.NET experience can create and modify web sites. If you have already developed web applications using the ASP language, this is a pretty solid basis for handling Sitefinity. There are a lot of controls which can be used only by installing the application, and of course, you can add your custom ones if needed.
The Developer Manual and User Manual contain a lot of information which cover almost every single module of the product. Also, you can refer to the Sitefinity Blogs on our web site: http://blogs.sitefinity.com/, where you can find additional useful information.
The Sitefinity Videos are also a good intro to Sitefinity, so can look at them if you haven't done so.
And, last but not least, we will be more than happy to assist you if anything goes wrong.
the Telerik team