You can do this. It's gonna be a pain, though. If it's a gas unit, find where it starts. Usually, in the boiler room. Hopefully, there is a valve and a union at the start of the run. Turn off the valve, disconnect the union, and cap the line. Best to start there because when you remove the unit, if there is a pipe sticking out of the wall, you can disconnect it with no worry of a gas leak in the wall after sealing the hole. I'd bet the facade around the unit is at best set in place and painted around, a small crowbar will do the trick. Then, look under the unit for where the piping comes in. Disconnect and remove any wall fasteners (doubt there are any). An extra set of hands will help. Also, cap the disconnected gas pipe. It's gonna smell. Good luck.