Your may need help. Put some tank water in a bucket and put your plants ornaments in there. Avoid letting anything touch air to minimize bacteria loss. Bag your fish. Remove your equipment (I'm hoping you aren't using a UGF) and put the filter media/bio wheel/etc in with the plants unless its a canister and then you can just trap water inside it. Drain the tank most of the way but keep the substrate wet. Put some water in another bucket or container (they are cheap at walmart) and move the substrate over (you may want to vaccum first). Again, don't let it touch air. Keep it submersed. Break down the tank and start the process in reverse to set up the new tank. Put the tank up and add about a quarter of a tank of water first. Then move the substrate back keeping it wet. Put your plants and ornaments in and set up your equipment, fill it with water and let it run for a half hour to filter the stirred up junk left in the substrate.
When your done, hopefully you will have a minimal if any cycle process. You will need to keep close track of ammonia and nitrite levels just in case but you should be alright. Put your fish back in last and you may want to acclimate them as if they were new fish.
You can try to save as much of the existing water as possible, but if you are going to reacclimate anyway, it shouldn't be a problem since your saving most of the bacteria. I would just keep enough water to keep the tank contents wet and replace the rest. Bacteria usually attatches to surfaces but only a little of it actually floats free in the water. You may want to add a anti-stress agent to the fish bag or even the new tank, this is optional.
