It's not difficult. It really isn't, but people struggle over it. Lots. Let's see how to make an image gallery in Drupal 7 (the same theory will hold for Drupal 6 and, I presume, Drupal 8).
Back in the good old days (circa 2008, Drupal 6.3) there was me. Me and my Drupal installations. And not much of a clue about anything. Then I thought, if only I had a WYSIWYG editor, my life would be complete. Then I tried to install one (TinyMCE specifically) and lo!, my nightmares began in earnest.
You want to upgrade your website from Drupal 6 to Drupal 7. The easy way!