I would transfer all of the fish and any other critters to a bucket, and drain the tank completely, maybe storing the water in multiple other buckets. You could also try digging a hole in one corner (or somewhere where you can dig a hole) and once the water is drained, let the remaining water contained in the substrate seep out of the substrate into the hole, then siphon that out as well (if that makes any sense). It'll be messy, but it might save you from a complete overhaul. Also, if there's any rocks or wood that can come out, pull that out as well.
And finally, get a few BIG guys to help you. They can lift a lot more, in my experience.
10 gallon acrylic fw planted. 6 neon tetras, 1 GBR, 3 Amano shrimp, 2 nerites, 1 BNP, Eheim Classic 2211, Finnex Planted+ 17W LED, Hydor ETH 200W In-Line Heater, InkBird temp controller.
10 gallon aquaponic setup, hydroponic basil, 8 HET rasboras, RCS, red ramshorn snails.