The back seat stays where it is. The back half of the exhaust needs to come out. You will probably have to unbolt the trans tunnel brace to do that. Then take out the exhaust heat shield and lower the tank. If you have an older-model tank, there is a vent hose running over the driveshaft. So you need to remove that while the tank is partway down. Also, you must remove the filler neck and vent hose. This is completely simple in theory, but the hose clamps are sometimes at very awkward angles. A small, perhaps 8mm, ratcheting wrench might help with those. Once that is all disconnected, then you should be able to drop the tank competely, remove the fuel and vapor lines, and slide it on out.
... There was a really good write-up on Rich Thomson's MN12Performance website, but that is down now. Some Thunderbird club out there (Cincinnati maybe?) has a mirror of it up on their site. Try to find that.