What you are really wanting to do is port databases and applications.  That is a lot more different than importing basicly text into an existing database.  If you are porting over TO DNN then you are going to have to set up your site and put all of the modules in place that you want. Then the hard part of moving the data over between databases Since your site is running php now I'm assuming you have mySQL as your database.  You will need to map all of the tables to the new tables that are used in DNN assuming you have a mysqldataprovider if you are going to use SQL Server that makes it even more difficult as you will have to export the data from mysql and then map and import it to the righ tables in SQL Server. 

There is no software out there that can do this for you as it is too custom a solution.  There are really expensive solutions to port from SAP to Oracle applications but it's really just a bunch of people coming in to do custom work. 

That said I've got nothing better to do and Those new Cessnas look really nice.  I'm sure we could work something out.  :)