Hi,
Indeed, it's a very complex task to try and digg terrain and create a realistic behavior for bucket loading/unloading and transfers.
For this, you'll very likely need some very complex algorythm to have your bucket interacting with the ground, so if you have no experience with c# and complex math, this is going to be extermly difficult.
I have tried myself and removed the ability to digg because even on the video you linked, I don't think this is realistic enough ( that's my personal test, it's still very valid for training and general feel for it).
http://www.fabrejean.net/projects/excavator/I wish I had an easy answer for you on this.. desperatly want to have time to work on a proper digging system in Unity.
If I had to develop this I would work with voxels, and particle simulation with blobs:
[url:http://forum.unity3d.com/threads/fluvio-fluid-dynamics-for-unity.95255/]Fluvio[/url] would be my first attempt at this
I know there are some asset for terrain deformation, and that's would be a good way without having to use voxels, but again, lots of crazy maths and handmade physics interaction for force feedback ont he bucket to prevent irealistic bucket movement when digging ( going side ways when half in ground, stuff like that).
Bye,
Jean