Toilet flange disconnected, vent pipe to tank disconnected, drain output pipe disconnected or cut. Remove fasteners on tank flange or supporting hardware. Tank should fall off.
For the new tank, they sell tank sealing "doughnuts" that compress around the various pipes and seal onto the tank. I relocated my toilet and vent pipe. I drilled new holes, inserted the "doughnuts" in the tank, lubricated the pipes and slid them back into the tank. The "doughnuts" were purchased from an online tank supplier and included the dimensions of the new holes for the size of the pipes being installed.
Good luck with your tank!
