So What I would do would be drain enough water out of the 46g so that you, with help from someone else, could lift the corners just enough to slide so furniture movers in under each of the four corners of the stand. Then slide the tank and everything over to another spot out of the way. Take the furniture movers out from under neath and then put the water back in the tank.
This will clear the spot for the new tank. You can then setup the new tank in the spot you want, put in the new sand and rock and get it running. It will need to cycle though, you really wont be able to avoid that, but you can speed it a bit by adding some Dr. Tim's One and Only bacteria, or something similar. But since the other tank is still up a running it will afford you the time to get the new tank setup and let it cycle properly. Once the cycle is complete you can then move all the inhabitants from your 46g into the new tank
For setting up the sump and skimmer: Is the tank reef ready or will you need to use an overflow box? Either way you will run the drain line down to one end of the sump. The skimmer should go in the first chamber (same chamber the tank drains into) and then you put the return pump in the last chamber of the sump and run the return line back up to the tank. Actually fairly similar to the canister setups in that fashion. If the tank is reef ready you can either use pvc piping for the drain and return lines or you can use vinyl tubing. For an overflow box you will want to use vinyl tubing.
The skimmer is fairly simple, you will just plug it in and then you will need to adjust it to get the bubbles to the right spot in the column. Also most skimmer work best at a certain depth in the water so you want to use something under the skimmer to raise to the right depth level. Many use egg crate stacked up. I made a glass box that my skimmer sits on to get it at the right height.
just make sure the dudes not a buckeye and you're straight!