I have just replaced the bearings in the w103 with the plastic outer drum,took me about 6 hours total.You need to remove the belt from the drum pulley and remove the two screws from the motor.Remove the three bolts that hold the concrete block on the top and remove the three wires on the back of the outer drum.Now unscrew the the bolt at the centre of the bearings holding the drum pulley on (this can be very tight,be careful not to damage the pulley) remove the pulley.You now remove the metal clamp that holds the removable plastic back,unscrew the clamp and remove the back+drum,getting this through the back can be awkward but it will come.Now you can remove the seal and bearings and renew them.Make sure everything is clean especially the large rubber seal on the plastic outer drum and put everything back together.
vince
September 2007