Will, everything is most certainly dead. Live rock has now turned to base rock and will need cleaning to remove all dead matter from it. The sand is helpful as it is pricey to buy. Just have to add a bag of live stuff. Depending on the type of skimmer that come with it, it is a good deal. But I realize Ostrow does not have much room. I'm still pushy sometimes though, Sorry Oz.
Water changes for large tanks.....
Well Ostrow, I have to add so much top off water for evaporation, that I don't worry about water changes too much. I use a 5 gallon water cooler type jug,(have three of them), to buy RO water, fill, and drain tanks when doing vacuuming.
I had a python system once, and wasn't too impressed by it. When I have to drain a large tank, I just throw one end of a hose into one of Patties flower beds, and siphon away! To fill, I have a NON-TOXIC hose for RV's that I use. It was pricey, but better to be safe than sorry.