There are a number of threads on the forum on this subject. Fishy Dave, Marlon and Mr PT amongst others have provided lots of information on fitting electric heated seats. I am not very technical and when I fitted mine these threads were invaluable. Pre-facelift cars usually have the necessary wiring in place and if that is the case it is just plug and play. If the wiring is not in place you will need harnesses which BMW no longer make. Fishy Dave’s thread gives the part number. They are hard to find but I got mine from a BMW dealer in Lithuania. I found it on the internet by putting the part number in. I have sold the car and haven’t kept all the details but if you search and find the necessary threads you should find all the information you need. Hope this helps.