Best advice - take your time assembling the cabinet, tank, and chiller - don't rush it and get it done right the first time.
Don't run any pumps without water - they burn out quickly running them dry.
Live rock usually 1-1.5 pounds/gallon (.45 - .68 kg/ 3.78 liters) A lot depends on how dense the rock is - highly porous rock would be lighter and less needed. It also depends on the look you want and how much open space you want left on the sides, front and back of the rock. Tough question to answer.
The amount of sand and whether you want a deep sand bed or not I'll leave someone else answer. I'd advise against using all crushed coral (the large piece type) as it's known to trap a lot of debris. Aragonite based substrate seems to be what most use.
Ok - time for more opinions from others!