Removing the overhead console from the headliner
To remove the overhead console from the headliner just pull the console FIRMLY downward. The Volvo manual DOES not specify how to do this (only says that a trained Volvo technician can do it) and VIDA only says to pull the console downward. I'll attach some pictures to show you how it's done - I didn't want to break my new ride so I hesitated whether to change the courtesy lightning on my own.
If the console has never been removed you NEED to apply some force to remove it. Don't worry about breaking the console - this should not happen.
After the console has been removed you should see the plastic framework in the roof with ONLY one connector and a few latches. I have marked the connector and one of the latches in the picture.
Soldering out old bulbs and soldering the new LED lightning in
To remove holder from the console just twist it out. You'll not be able to remove the bulb from the holder easily, however. You need to somehow break the bulb's wires to pull it out.
The rest of the soldering process includes pulling out LED bulbs from their holders and putting them into the old VOLVO's holders, soldering the LED's wires to the old Volvo's metal connectors and putting the holders again into the console.
I leave the decision as whether to buy the holders from ebay or customize them yourself to you.