even i am new to frame buffers but of what ever i know i'll share it with u..
first of all its really simple to apply a geometry shader to the cube ...
this has to be done for mentalray versions bellow 3.6 ( ie before maya 2008)
to assign a geometry shader
do these following steps
1:) create a dummy cube and open the attribute editor you will be in pCubeShape1
2:) to the left of this tab is pCube1 select that tab this is your transformation node
3:) open the mentalray option in that you will find geometry shader
4:) enable the geometry shader and assign p_MegaTK_pass here (which you will find in the hypershader----mentalray shader option------ geometry) ..
i hope this solves one of your problems.....
also remember all the function of puppet shader are inter connected
(atleast thats what i think )
i mean if you connect the light and not use the shader itself it may not work...
one more thing every object need to have the shader otherwise it will not generate the frame buffers...
this shader doesnot work on objects where faces are selected and textured...
for ur scene its better you assign the puppet shader to the objects and give the attributes the same values what you have given in the maya shader ..
leme know if this works