There is considerable documentation available for users who are switching between any operating system, and you can find lots great online articles, published books, and in-depth tutorials.
For switching from Windows to the Mac, you can buy a support plan from Apple which allows you to go in to their stores several times and get training sessions from their experienced employees. This is an especially good for less technically-savvy users.
Because Linux is open source and community, there isn't specifically anyone to go to for help. Ubuntu does offer tech support for a fee, which is one option to consider. They also have a very active developer community which participate in online forums, and you can get lots of help by asking questions there.