If a sucessful website decides they want to change their platform and switch to a modern cms system like DNN.  What Roadmap is availiable to guide folks through the difficulty of syncing DotNetNuke with existing external databases.    

DNNmasters does have a module which takes you half way there but reguardless this is quite a complicated process to sync to existing user profiles during a transition time.  Are their built in solutions be being able to update users, through the Microsoft Membership Management Table System.  Is their any full examples of how to sync db's outside of DNN.  

Is their any tutorials about using IWeb methods or UserInfo Methods from in or outside DNN to change user information.  I do not have the kind of time required to figure all this out by myself.

i recently did something simiar for a customer and it wasn't hard at all.  they had an existing website site based on asp/access.  first, i converted the access database to ms sql server dnn table.  i then created a module that loops through the converted table and creates new dnn users.

The free opensource SSO module might help you.  At my work place, we switched from a Coldfusion based intranet to DNN.  During the migration period, the SSO module allowed users to login the new DNN portal using the existing user accounts in the old intranet.  The SSO custom user profile screen let users updated user profile in DNN and the changes were pushed into the old intranet database (in realtime).  The module import utility were used to batch import accounts/assign roles into DNN.  You find the module documentation in the  Wiki at our site.