Gregers,
thanks for dropping in.
i will leave the field ope to our Braille Scale crew,
but i think you want to build & paint, or paint & build the interior first,
then do the rest around it, kind of like the cockpit of an airplane build.
that is what i am doing on my 1/35 Quad.
usually armor or vehicle stuff is painted mostly assembled.
on the topic of buying a kit that you already have because you don't want to open the first one:
not me personally, but i think you will see that most forms of
modeling madness manifest themselves here.
:-)