Double glazed unit in PVC door. ?

Hi.
I have a small double glazed unit in a pvc door that has been broken. The glazed unit is above centre (rather like at a spyhole height) and has no beading around it.
How do you remove these units for replacement?
I am thinking the whole inner door section has to come out fir starters as the only beading is internally around the whole frame. Is the inner frame sandwiched together ?
Does anyone know :-)