Just to be clear.. you want to have your water mixed and ready to go before the LR arrives. Do not add water and salt to live rock otherwise you will kill everything on/in it.
If it was me, I would pick up the sand I want to use and get through the long arduous task of rinsing it in tap water until it runs clear, get that in the tank first. Mix up your saltwater and put that in, get your pumps running etc to make sure everything is operating properly. Have the heater on, and water at the right temp. If you're worried about pests, it will be easier to examine the rock in your tank for a few days. Move the rock around and see what you want to remove, if anything. Then once you're happy you can start aquascaping.