Just my opinion, but I think you would find Trapcode Form an easier way to go about attempting this project. Check out some of the tutorials over at Redgiant, Text to Sand should give you a good starting place, change the particles to custom particles and some manipulation of the layer maps should do the trick.
Johnny Cuevas, Editor
Thinkck.com
“I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work.”
—THOMAS EDISON on inventing the light bulb.