To answer your questions corrently we would need to know your filtration?
Example, if you have solely UGF, then yes you will more than likely recycle your tank. In most cases you bacteria live in a canister, HOB or SUMP so you would not have to "recycle" your tank if you switched. Just do not do any maintenance on your filters before the switch or for a couple weeks after to avoid any ammo spikes. You are removing some surface area from the aquarium along with some bateria but 90% your colony lives in your filter (excluding UGF)
After you switch it's easy, just use your gravel vacuum and hover it over the top of your sand to pull off anything from the surface. WASH the sand well before putting in your tank.