Conforming particles to mesh object

[Billabong]

Hello. I am trying to reform an object from particles to a cloned object. Basically I have 2 of the same object/geometry. One of them is behind the Cyc wall and unseen from the camera. I want to have particles, not geometry in the form of the object behind the wall and have those particles  come from the left and right and top to form the object in front of the camera.
  I've been working on using set target and find target and Im slowly getting there, but I do have a question or two.  
  I don't want the transition from the object to be actual geometry but rather particles that turn into Geometry once they reach their target. How should I go about trying to achieve that? My last question is,  I want the transition to be quite dramatic, almost like a tornado or vortex happening  and from it , it starts forming the actual object. Is this possible? 
  Thank you so much for any help.

[Alexx31]

I have experimented with something similar some time ago.
I could imagine without trying and details could be different:

Original object, make a copy of it, which is invisible but at the same location on frame1
Then > Face Fracture (turns all faces into particles but keep it as it is)
Spawn once into new event. This creates a clone (child of each face)
Assign a different shape to each particle in the new event.

Find Target: Easiest would be to use the parent, because then you will have the exact location on the object.
So at frame 2 place your invisible object where you want the new particles to fly to.
(enable using original animation).

Then it is all about finetuning the particles, setting turbulence and morphing their shape back to the original.
Also a shape can be animated.
It works, when all faces need the same final shape (e.g. a honey comb topology, otherwise I don't know how to store a final shape of a mesh face and gradually morph into it.).

- Or you could also store individual scale values of each face in a "custom properties with SET" and then randomize their scale and then gradually get back to the size.

Have also a look into this tutorial from Simone, which has a different approach, but the object is the same location here.
https://www.youtube.com/watch?v=29KUXU4PaC0

Let me know what worked for you...