Not familiar with your specific machine, but I'll try to help anyway. Is this an umbrella style tool changer? Anyway, your tool change position is usually the machines zero position, G28 X0.0Y0.0Z0.0 will move all three axis's to the machine zero position for a tool change. Be very careful using G28 with all three axix's referenced on the same line, if there are fixture clamps or if your at the bottom of a pocket all three axis's will move at the same time, usually causing a crash or at the least breaking a tool. Here is an example of how I would do it.
G00Z1.0 (MOVES TOOL 1" ABOVE PART)
G28 X0.0Y0.0Z0.0 (PERFORMS MACHINE ZERO RETURN ON ALL AXIS'S)
G80G49G94M01 (SAFETY LINE, IE CANCEL CODES)
M5 (SPINDLE OFF)
G00G40G49G80G90 (SAFETY LINE FOR NEW TOOL)
T3M6 (CHANGE TOOL)
S5000M03 (SPINDLE SPEED AND DIRECTION)
The 1" above the part is a good safe distance, you would need to go higher if you have clamps that stick up higher than that 1". Is your tool carousel mounted at the front of the spindle? If so you probably dont need to use G28 instead you would do something like this with G53.
G1060T0.2D.500S0.05L0.075J0.2K0.015H0.F30.V30.E15.M100.W2.C0.1P3.R0.1Q3.X0.1Z2. (FANUC'S CONVERSATIONAL LANGUAGE)
G1220T2.B0.L-0.2H0.375V0.2U0.75W0.4R0. (FANUC'S CONVERATIONAL LANGUAGE)
G00Z1.0M09 (G00Z1.0 NOT NEEDED, I JUST USE IT FOR ADDED SAFETY)
G53Z0.0 (MOVES Z AXIS TO MACHINE ZERO FOR TOOL CHANGE)
The G53Z0.0 returns the z axis to the machine zero posistion for a tool change, some tool changers don't need the X or Y axis to be in a certain position. This is true on some of the smaller machines that have the magazine at the front of the spindle. A photo of your machine showing the location and type of tool changer may be helpful.
Use any info provided here carefully, it is only a guide to give you an idea of how it may be done, machines do differ from different makers. Ideally you should order the manuals from Hyundai, it's money well spent when it comes to safe operation and maintenance. Below is an example of a tool changer at the front of the spindle that the G53 method is likely to work for. Hope this is of some help to ya.