Maybe I am best showing you another site which has achieved closely what I want to achieve.
If you look at this site you will see the thumb nails, and when the user clicks on them the top image changes. How are they achieving this, I notice theres no # in the url, but its not loading a whole page each time.
Basically I want what they have. However, with a few modifications. I will be having categories for the thumbnails which can be changed dynamically on the page. I will also be keeping my fade and scroll to animations when the user clicks a thumbnail. Also when the user first goes to the categories page they will just see thumbnails and not a default large image and description. Basically how I have it working on my site at present. I prob am doing it totally the wrong way, which I realize now. I just stumble upon these tutorials and think great this will work for me, but its never that simple :(