i wouldnt modify my own hinge...unless you are very mechanically inclined i wouldnt do it if i were you. the possiblity of your hinge dracking and your door falling off isnt very pleasing.
although it is expensive (1400 for decah) its well worth it because the quality is assured. if that price is not for you, then i don't recommend lambo doors.
but thats not for the celica
i wouldn't try making it your self, do have any idea how much a new factory door would cost, not to metion injuries you could have from a door falling on you