Utilizing private methods/vars inside module
Yes - it's that simple. Remember; Drupal is only PHP.

Although your class should be called MyClass.php rather than MyClass.class.php to adhere to the Drupal Coding Standards for OO code (note - this isn't explicitly declared, but is hinted at when they describe the Interface file naming conventions).

Just to pad this out a bit; you could also use the X Autoload module to allow for PSR-4 style autoloading instead of adding your class in the files[] array. I do this for as much D7 code as possible now (where I'm not using Composer Manager), and would whole heartedly recommend it.


  xautoload is a comprehensive and yet highly efficient PHP class
  loading suite.
  
  Most importantly, it provides Drupal-8-style PSR-4 (and the old D8
  PSR-0-style in "lib") autoloading for Drupal 7. But it is also a great
  tool for 3rd party autoloading.