I have a Zaf A 05, just put in some full leather GSI seats from an '03 model. Only had wiring under the seats for the seatbelt tensioner. However the missus is interested in getting the heated seats connected. What's involved, what do I need to get? How difficult is this? Which plugs on the seats are for heating, grey, black and/or yellow? Does it need tech2? Any guides around?