you would have to store it in warm salt water otherwise all the benefical bacteria on the rock and will die so you would have to cure it again.
but i would check with CHAC as he knows a lot.
i think its probably best to wait till i have the tank up and running before i buy it, its just if i wanted to buy the rock beforehand i can get it today as im travelling past the LFS which is 30+ miles away
i think if you buy cured rock and dnt add it to a tank pretty fast you will get die off and then it would be uncured rock and you would have to cure it again in your tank
I have stored Live rock in a poly box for a few months with no problems
I used some old tank water (from a water change) a heater & a spare powerhead
Lighting isnt a real concern as long as you provide heated salt water & some circulation it will be fine
Best thing to do is add a pinch of food to the water every week or so, just to give the bacteria some for of food source or add a frozon prawn to the water & let it break down this will produce Ammonia & Nitrites thereby feeding your bacteria
PS a 1/2 Hour drive wont do the rock any harm - ask your LFS to wrap in wet newspaper (they probably will anyways)