Electric seats

[Apansson]

Looking to replace textile seats for some leather ones. Today the seats are heated and manual. It’s quite hard to find manual leather seats. Are electric seats plug n play?  Is it any problem to program these to the car at the dealer? Car is an XC40.

No it's not plug and play in your case.  Since your current seats are manual, most likely either you do not have the seat controller at all or bunch of missing wiring.  
If you purchase used seats make sure the airbag is not blown and have the controller under the seat. Then you 'll need to wire the missing ones (depending on the features of the used seat)  then you will need to enable those features from the orbit.

Is there anywhere wiring diagrams available for these cars? Earlier models were widely available on internet. I’m thinking electric seats without memory might could be working since I got the heating? There’s a module under the seat, at least for the heating.