If this unit has been put together in usual SF manner, the body is glued to the chassis. Usually done with impact or UHU adhesives, so out with the scalpel and cocktail ticks to open it up- insert the scalpel in the join of body and chassis and carefully slide it along to try and cut the glue, as you proceed insert the sticks behind the blade as you move along. You may find molded parts in the join on the body side which will hinder the blade- their push-pull unit had four of these, 2 on each side, force will break these so go carefully.......
You can see the broken moldings on the chassis edge here on the DVR
I installed a NS angle at each end of the body with a captive nut soldered in, to screw the chassis back on, allowing for easy opening up in the future.
Eoin