accessing xml in C#

In a C# 2010 desktop/console appplication, I would to know how to accomplish my tasks (or at least part of my taks) listed below working with xml:
1. I want to parse out specific nodes so that I can access the various level of nodes I am working with.
2. I would like to place various data elements in a collection/array that I can work with like an array.
3. I would like to take the xml file and add certain sections to a sql server 2008 r2 database.
  **Note: The xml contains the various kind of stuctures:
    a. There is an occurence of  0 to 50 customer names.
    b. There is a node is just unique elements.
    c. There is an occurences of 0 to 25 elements that contain the
       following 4 items in each occurence:
       customer number, customber address, customer city state and zip,
       contact name, contact number.

Thus can you tell me and/or point to to references that will show me how to accomplish my goals (or at least part of the goals)? If I have at least an example or two to look at, I can figure out how to accomplish the rest of the goals.