I have replaced the element twice in my car ( long winters up here).
Look at the fuses first as mentioned and look at the relays located under the drivers seat too ( I had a bad one once).
The wire loom runs down the back right hand corner, if you take the connector apart and measure with an ohm meter it should be around 30 ohms (from memory) if the element is gone it will read infinity ( dead short would have caused the fuse to blow).
Theres actually 3 elements in each seat and both times it was the bottom element that failed (most flexed I guess?).
It takes about 2-3 hours to complete this job as theres a lot of tech in our car seats.
The air bag and seat belt are both mounted on the seat along with the seat controls and all the trim pieces.
I can help out and answer any questions anyone has if they want to try this.
has heated seat kits I think?