You can also get a new trash can (plastic). That would be a lot cheaper. Unplug the heater. Syphon 3/4 of the water from your 55 into the trash can (or whatver amount you can get in without getting too close to the top), then transfer your heater and a bubbler to the trash can. If you are careful, the heater setting will not be disturbed, and it will hold the temperature for you. Check it a few times over the 1st 2 hours and adjust as needed. The trash can can work as a temporary home for a couple of days as long as you have vigorous aeration.
Now move your 55, clean and or replace the gravel, clean and replace all filter media and re-charge with fresh water. Add in stresszyme and any other preparative water chemicals (e.g., pH adjustment, etc.) and let sit for a few hours. Move your heater over whenyou are close to making the switch. Make sure the temperature in the newly set up 55 matches the trash can. Once the 2 temps are identical, move the fish.
When you are done, you'll have a new trash can you can use.