You can buy seat ventilation & heater kits complete with nice switches & are easily installed. Most importantly, if your seats do not have perforated inserts then forget the ventilation part as it wont work but the heater will. To get the best out of ventilation is to use good quality foam for the cover & punch 1/8"(3MM) holes in the foam before sewing the perforated leather on. These holes should be punched above where the fans have been set in the seats. Note, dont punch too many holes & too close together as it may distort the leather when you are finished. This process can only be done if you are making new covers so if your using original covers then the ventilation will still work but not as much air gets through the foam. It is a relatively easy job & you can make good money from it.