I
am planning to do the replacement as well and wonder when it will
be available. I have a factory panel some guy had in his garage
I got on e-bay (lucky me) I am the original owner of a early 260z
40k miles. It runs great but have to do cosmetics.
Bill D
Greenbelt MD
Bill,
Not sure when the tutorial will be up, but actually the procedure
is simple, but time consuming. It took the person in my photo documentation
over 5 hours of paint removal and spot weld cutting to successfully
detach a good panel from the car depicted in my preview
photo.
Use high strength air craft paint remover and swab it on to all
areas of old panel being removed where you suspect spot welds
to be (there are many and not in any exact location. Study the
bright dots on car rear area in my preview photo for number of
welds likely to be encountered.)
Next, use wire brush on electric drill to remove paint down to
bare metal andthen use center 
punch
on each spot weld found to stake a center mark for spot weld collar
removal tool's centering needle. Spot weld removal tools have
a collar-like cutter with a center guide needle intended to align
tool to center punch mark. Make your center punch marks with care
because a spot weld cutter cutting into the actual spot welded
steel area will dull down rapidly because spot welded steel is
quite hard compared to the original soft sheet metal.
You can buy spot weld cutter tools in auto body shop supply and
tool stores. Buy the best quality steel cutter available because
cheap ones will dull down to ineffectiveness before you get the
panel removed. Even with highest quality cutters, you may need
more than one new one to finish the job.
Carefully use the spot weld removal cutter to cut through the
outer sheet metal around the weld 
and
then repeat until all have been cut. On the inside of the car,where
the back panel meets the body at the deck, Nissan has applied
a strong, but pliable mastic sealant that will have to be cut
away with a mat knife before you can pull away the loose panel.
(Photo on left) Remove old panel
carefully without prying or force until it comes away from rear
leaving the view you see in my photo.
Below is sample of another removed panel showing typical number
of spot welds Nissan used on the S30 body. Notice that they are
in a non-aligned, somewhat ranom order making them a bit difficult
to find under body paint without using paint stripper.
Before
you can install the new panel, you will need to carefully grind
down flush every spot weld nip left behind on the car body and
then wire brush and chemically seal all rusted areas. Of course
any rear area body damage that will prevent proper alignment of
new panel must first be addressed also.
For installation of the new panel, consult with a knowledgeable
body man about best methods of welding in and sealing the panel
to the body. Most likey he will express the greatest concern for
how well you have treated any surface rust and body rot in the
rear area before attempting to attach the panel.
--Eric Neyerlin
Panel
Removal Procedure outline
