Firing up a setup for the first time in 3 years.

[BlueTang<3]

I would probably pressure wash the rocks and then place them in a tub and do a few water changes first, I imagine you'll have a pile or phosphates leech from the rocks. As for the sand u could wash it or just it only one bag might be just as easy to get new stuff. Once you get set up there a few ways to get it going, I started my new tank with dry rock and used zeo to cycle it. But you could use probio or other products. Might be just as easy to get some live rock from some one and seed your rock to help it along. The easiest way is to probably throw a shrimp from a ring in there and let it cycle the tank.