Here goes the solution I found to replace the guides without opening the motor: all you need is a pair of vice-grips:
Remove regulator from door and place it in its half-way position:
Use the first vice-grip to grab the upper grey cable..go ahead, you won't damage the cable just by crushing it, do not worry.
Now join the 2 cables with your fingers, this will compress the cable springs at their maximum
, and at the same time use the 2nd vice-grip to grab the black cable, as close as you can from the upper white cable guide border:
Remove your fingers from the cables, they will now remain loose:wink:
You should be able to remove the cable from the thingy part...if not, you can always unscrew the pulley or just loose it from its position.
Finally, when cables endings are removed from the lever, pull the upper white cable guide from the regulator track, with the 2 vice grips still attached:
, and you can now replace your old rubber guides by the new Teflon ones without opening the motor and thinghten the cables again.
Hope you'll find it useful, have fun!