Peasely I just did the exact same thing your doing 2 days ago. Im not sure what size tank you have but mine was a 55 gallon. Heres what i did, took 2 1/2 hours.. First I went to my local wal-mart and bought 2 huge plastic garbage cans, they were 26 gallons each, now that only equals 52 gallons but if you have alot of live rock that will take up the extra space. But anyway, while at the wal mart i also picked up a 15 foot garden hose. Now I got home and stood both garbage cans up side by side, stuck one end of the garden hose in the tank, and the other in the garbage can and started the sucking . Lol that water tasted horrible, but anyway after about 15 minutes if that one garbage can was full and another 15 minutes the tank was pretty much drained.
When the tank was almost drained I plucked the fish out and put em in the first garbage can that was already full, also removed all the live rock and corals and stuck them in the other can. Once this was complete i then begam removing the CC out with one of those little plastic shovels you can buy in the toy section of wal-mart or any store with toys. Then after all the crushed coral is removed you will notice a nice pile of mud at the bottom of the tank, i removed it with paper towels. Ohh one thing i forgot to mention was you will find all kinds of living things at the bottom of the tank in your CC, i found some big worms and put em back into the new tank with the sand.
Ok now that all your crushed coral is out and your bottom of the tank was cleaned add your sand, not water or fish add the sand. Now after the sand has been added and you smooth it out and make it look all nice and neat goto the dishes in your kitchen and grab the biggest plate you can find. Food plate.. Place this plate on your sand and begin pouring the water in from your garbage cans, you will have to use a smaller bucked to get the water out of the garbage can since it will be too heavy to lift. Now when you pour the water into the tank make sure you hit the plate first and not the sand, with the water thats coming out. Continue to fill your tank, add your live rock and corals then your fish. Then your done. Thats it simple as that..