The plastic pin is actually 2 plastic pins one inside the other, they
are really like roll pins and you need to tap them into the door with a
hammer and pin punch then after you have removed the regulator plate you
can recover the pins. To re-assemble the door you need to gently tap the
pins into the glass before you put the glass into the door and then the
glass pushes down until it locates in the regulator.Also I think that
the door catch is attached to the plate and you need to remove the door
handle ( to remove the door handle use a T20 screw driver to unscrew the
small screw in the back edge of the door whilst holding the handle out
and the fixed part of the handle can then be pulled out then unclip the
small cable from the handle and pull the handle back and out of the
door, the handle frame can stay in place inside the door skin)and the
three bolts holding the catch before the plate can be removed completely