Techno:
DNN is a very sophisticated (and complex) framework that indeed makes your life easier when you need to implement heavy duty sites quickly. However, I would recommend that you learn how to develop ASP.Net applications from scratch. Since you are a college student, you should learn the basics very well. This will help you with two things. First, you will be able to understand the DNN architecture a lot better, and second, you will be able to appreciate a lot more what DNN can do for you. Once you know the basics well you will be very effective in creating modules and you will see how quickly you can take advantage of the DNN architecture.
For instance, you can buy one of those books to learn ASP.Net in 30 days (version 2.0 of course) that follow a project from beginning to end and you will see what is involved in creating a security architecture for user accounts and access control, a menu system, a standard approach to data access, and a modular approach to achieve consistency in the look and feel of the whole project. These are the areas where DNN shines. By the way, if a customer asks for 100% original work tell them that you can do it but it will cost them more (it is actually a lot of work) and will not be as reliable or polished as a solution that is being used, tested, and debugged by a few thousand knowledgeable people.
As usual, don't try to cut corners, learn the basics well. And also, in case you wonder, <prepare for the flames>, you can do the same exact things in C# and VB.Net. All the arguments about language power, speed, object orientation, etc. etc. are not valid in the .Net world, they were very true in VB6, but not any longer. Choose the language that you feel more comfortable with. Bear in mind that DNN is very complex, robust, and flexible and it is all VB.Net.
Good luck.
Carlos