Crushed Coral isn't that bad, honestly. In my experience I have used crushed coral every now and then with pretty good results. You have to do more frequent water changes and it's easier to gravel vac every couple of months...
If you really do want to make the switch though, I would take out a cup or two of the crushed coral out of the tank each day until it was all relitively out. Some will probably be left, but that's not that big of a deal. Then, before you add your dead sand, wash it completely in a bucket until the water is clear. If you are going with live sand (which is technically alive, but relitively inactive) drain the bag completely of all the water so that you get all of the dust out. Then slowly add it cup by cup to the tank.
It is a good idea to turn off your powerheads and pumps while adding the new sand. You will actually start to notice that your tank will be a little healthier and coralline algae with start growing faster and that your nitrates will be lower.
I have a 55 gallon tank right now that had crushed coral in it, and I wanted to add live sand, but I didn't want to take the trouble of taking the crushed coral out. I just added 10 inches of sand on top of the crushed coral, and it's doing wonderfully.
Right now though, every tank that I set up is bare bottom. That is because I like a lot of current in my tanks, where the debris, detritus, etc., will always be kept in motion and I don't have to worry about blowing the sandbed everywhere.
By the way, you do NOT have to have a sandbed because of beneficial bacteria. Bacteria live in the live rocks, in your filters, in your pipes etc. Sand beds is just another way for bacteria to break down nitrate into less harmful gas.
I hope this helps.
