3D particles from imported mesh...

Hi there, I did a search on the Facebook page but found it difficult to find anything.
I want to import an a 3D model and then use it to create a particle system based around its 3d shape, ie so the particles move around the shape of the object.

Any way to do this? Or is it easier just to make a particle system from a similar geometry shape in TD? Basically, I want the original model appearing and vanishing and the particle system taking its place as it disappears etc.

Thanks!