this is a relitively easy procedure if your mechanically minded allthough you will get greasy fingers, you will need to remove the interior light, release the motor from its fixings-torx 25 i think, there is a spacer on the centre screw (dont lose), the rails are held in place by 3-4 torx screws, pull out rails, it is advisable to replace the runners as a pair, when refitting the new ones they will come in the open position, you need to insert the cables and align both runners so they are in line with each other, then refit clamps and screws, oh also first thing you need to do is remove the glass that is held in by 6 t20 torx screws