But you may not have to remove the refrigerator. I have had success in doing it from the exterior access port, but that very much depends on the specific AS you have.
Look at the boiler tube (the vertical metal tube on the right side (from the rear) of the refrigerator. You will see a set of wires (maybe in a flexible tube) going up to that boiler tube. Uncover what you can and there should be a stainless steel pipe about 3/8 inch diameter, with wires coming out of the end. That is the heating element. It has a 90 degree bend in it. Work it up vertically from the well that it fits in. Once you get it out, put the new one in where you removed the old one. Done.
Now, that sounds simple, but often they are rusted in place, or have burned out in such a way that they have welded themselves in place. It is those which are really nasty to remove in a confined space behind the unit. That is where TG T is correct, very hard to do without removing the refrigerator.
Best of luck, may be easy, may not.