XC60 retrofit - seats, steering wheel, battery

[IMAY2023]

Cool, thank you for the prompt reply!

Can you please tell me more about controller needed for heated seats? And is there an easier way rather than tapping into CAN cables and/or adding new wires in pre-existing connectors? How can one check if he/she got lucky and got the cables? As I've seen that "older" SPA models got some wiring for other stuff, which helped retrofit greatly while newer ones did not. (I think I remember seeing something about such case here on this forum few days ago, but I forgot what exactly did it talk about as I've read a lot of different things for the past few days and things got mixed up. )

If I remember correctly, heated seats are part of climate control module (CCM). Each seat has it's own controller connected to heating pads, power from fuse box and LIN communication to CCM. I have heated seats at the front but not at the back. I explored the option of retrofitting factory heated back seats and it really wasn't worth the investment. 
You have 4 options. 
1) Cheapest, order generic seat heat and fit them into your existing seats. control them externally.  (cheapest)  around $100 USD for all parts (back and front) + labor you are done. 
2) Purchase the factory heating elements, controllers, seat climate button if you want back seats too, fit them into your existing seats. wire them to CCM, heating elements and fuse box)  expensive and hard work to put the heating pads into seats. finally enable from Orbit. 
3) Replace your existing seats with a factory heated ones from a junk yard. But you'll still need to do wiring to CCM, fuse box and enable from orbit.  (might end up more expensive than 2 above) 
4) sell your current car and buy a new one with factory fitted heated seats.