I went to the local rental yard with the 3.5t mini in mind just to see prices. 380 for the 3.5, but they recommended 5.5 with a 3' and 18" bucket, which would put the price with delivery at around $1000 per day. I can haul the 3.5 with my truck but not the 5.5. Is the bigger one worth the extra $600?
As far as the stones, they are mostly softball sized cobble with some larger and some smaller. As far as the dirt, I we have to back-fill 6" and I imagine that we might throw the rest of the dirt, minus the cobble in the back of the truck, might talk to a friend of ours who has a skip loader and skid steer and see if he would help us. He comes around periodically to do stuff that is too big for our tractors