I guess this really depends on your current knowledge with Flash, and/or your ability to tinker with programs. This is our most asked questions so I will break up this question in two parts.
When all you really want to do is modify existing images, text, and colors. Some of the elements can be editing right from the stage, while other elements you have to find in the library to edit. Overall, this is an easy task for people that have no knowledge or very little.
Changing buttons around (position), and moving sections of the template around, basically changing the foundation.
(Adding brand new sections to the template, embedding video, and recoding the template to move satelites from outer space.
Most of the people we find fall between Easy and Intermediate. From our experience people that have had no or little experience had no problem changing the template to thier liking.