The runners on the 3 door are the same as 5 door.
The covers come off with the foam padding attached and is quite easy to do so, would take a couple of hours, if that, to change.
The rear seat fittings are the same on a 3 door to the 5 door as well.
When removing the seats remember to disconnect the battery as you will need to disconnect the seat belt pretensioners, if you don't it can lead to a fault being registered to the SRS ecu and the SRS light will stay on.