I switched a while back. You might do a search and find some threads, but if you don't mind I'll give you the rundown. This is, in my humble opinion, a good way to do it.
Get clean Rubbermaid (or whatever) plastic tubs. Sturdy ones are good because of the pressure of the water pushing out the side of the plastic. I had to have three. Start siphoning out the water, WITHOUT STIRRING UP THE BOTTOM! When you get enough to cover it in the tub, start transferring out your live rock and/or corals into the tub. This goes much smoother if you have someone to help you. You'll have to work this around what kind of livestock and how much rock you have.
Once you get the rock and corals out, plus whatever inverts you have, start working on the fish. Try hard not to stir up a bunch of crap when you are doing all of this. Put the fish into their own container. Then I dropped the powerheads into the tubs to keep water moving good around everything. Then I just scooped out the crushed coral, cleaned the inside of the tank and all of my equipment completely, rinsed my sand (which you may not have to do with live sand, I'm not sure) and added it in the tank. Then I put in 20 gallons of new water, so it was like a water change, and started syphoning the old water back in from around the rocks. I had to steal some of the fishes water to cover all of my rocks, but not too much. Then I stuck the fish back in and filled the tank back up, plugged everything back in and Viola! There it was. The water was only cloudy overnight. By the next day it was clean and beautiful as ever!
I hope this helps and that you don't have any trouble. I am thrilled with the change. Good luck!
