I added seat heaters to my wife's 2003 ZX5. It took about four hours. A month ago I added heaters to her new car, a 2006 fusion. That took about 8 hours! It's not that difficult a job, it just takes a long time if you use great care. For the fusion I had to remove the seat and disassemble (it has side air-bags and 6-way electric). The focus was much easier (no air-bag, manual adjust).
I say go for it!