Very nice pond, pretty fish too. To do this you need to set up something to keep the fish in during your build. You will need some good filtration and water for those fish, they are nice sized and a lot of them. Others that have koi can tell you the minimum you can get away with during the move and build.
That is great the pond owner will help with the reassembly. Get your hole dug first, before you even begin the move, stating the obvious lol. Don't clean the liner at all, well you can rinse it with pond water to remove any collection of muck. But you want to keep the fine algae in good shape.
If you are on city water, have plenty of de chlor to treat the water as you fill the pond.
I would not put the river rock back in the bottom, leave it empty of rock, easier to keep clean. Seven pallets of rock is a lot of weight, either a lot of trips or a big rock moving truck.
The main issue you have is keeping the fish safe during the filling of the pond, getting the new water in the pond stable. You didn't mention the filters, it would be best if you can keep the media alive and in good shape.
A lot of work coming up, but it sure will look great when you are done.