I think the calculation for sand is 1 lb per gallon for 1" depth or something close to that. Of course, the dimensions of the tank will play a big part in that. i.e. a tall tank. It works pretty well on standard tanks.
Most live rock is packed wrapped in damp newspaper then placed in a styro box. The newspaper holds moisture and provides a little cushion. You can use a rubbermaid container or clean garbage can (one that hasn't been used for trash) and put a little water in it to slosh around to keep the rock wet if you prefer not to use newspaper.
Moving is always a good opportunity to do a significant water change, so no need to move the entire 55 gallons of water. 25-50% max is all that is needed. Clean garbage can with lid is easiest way to move that as well.
Remove ALL the substrate and live rock from the tank before moving. DO NOT move a tank with substrate/decorations/live rock in it!