Per Hyundai, the proper method of changing the fluid is to use a fluid exchanger. This is a machine made to tap into the cooler lines and replace all of the fluid in the unit.
You can alternatively disconnect a cooler line and run the engine for a minute or less to pump all the fluid out.
I would recommend the machine do it.
Hyundai does not have a procedure for your Santa Fe to service the fluid via dropping a pan and replacing a filter.