seat heater
If the heating elements need to be replaced, It is pretty time consuming- I did mine last year and was surprised at how long it took. I have had pretty many seats apart over the years, and occasionally stitched up new upholstery, so I am somewhat experienced in seatology. If you have never done this before, it might take a half a Saturday, although it isnt really complex. If you are used to tinkering, go for it.
Martin