I've repaired a couple. No big deal.
You should be able to unplug the seat and measure for continuity- unless you have back heat and that's still operating. If it's open you need to replace it.
Pull the seat out and open up the d-ring clips that hold the cover to the frame. Some also have a plastic U-channel that grips the frame as well. They're easier to take off than put back on- do it in a warm place- makes it much easier. You don't have to take the cover completely off- usually if you get the front and sides loose you can do the repair.
Anyway, the elements are typically under a spun fiber pad but on top of (or slightly embedded in) the foam of the cushion. Pull it out, Use 3M General Trim Adhesive (make sure to follow the instructions or it'll slip)to secure the new element and replace the pad, then put it back together and reassemble.