If you can afford to have a trainer then great, it is good to have someone to answer questions and save you some time. If you can't afford that then I have found the following tutorials have been able to get most .Net programmers up to speed with DNN in 1-3 days:

• Creating a DotNetNuke Module using LINQ to SQL (VB and C#) (Start here!)
  • Set up module
  • Create the table
  • Create the LINQ to SQL Class
  • Connect GridView and formView to LinqDataSource Control
  • Create the Code Behind
  • Create the module definition
• Creating a DotNetNuke Module using LINQ to SQL (VB and C#) (Part 2)
  • format the dollar amount properly
  • Validate that a description has been entered
  • Give the administrator the ability to add and delete Categories
  • Show the number of items in each category
  • Do not allow a category to be deleted if there are items using that category.
• Creating a DotNetNuke Module using LINQ to SQL (C#) (Part 3)
  • Move Add and Edit Items to a separate page
  • Use a ListView to implement grouping

And then have them read this:

• Introduction to DotNetNuke Module Development
  • What is a DotNetNuke Module?
  • Installing a Module
  • A Look into the DotNetNuke Module Definition
  • A Module Can Have Multiple Instances
• Connect Your Module to the Database
  • Using LINQ to SQL
  • DotNetNuke Linq to Sql Model Adapter
• Using the DotNetNuke API
  • IPortable: Easily export content from your module to
    deploy on your production server (VB &C#)
  • ISearchable: Easily Make Your Module Searchable (VB &C#)
  • IActionable: Add Items to Your Module Menu (VB &C#)
  • NavigateURL: How to make a link (VB &C#)
  • Module Settings and Personalization:
    Easily Store Data for Your Module (VB &C#)
  • Localization: Easily Translate Your Module (VB &C#)

DotNetNuke® Advanced Sample Applications:

• Simple Survey