take off all the oh sh!t handles, the sun visors and holders, pop out the sunroof switch and light panels. then open the sunroof and see if there's any little screws holding the headliner to the sunroof frame. also the a, b, and c-pillar trim panels come off. then it should drop down, bring it out the pass rear door.
have done a few, but not on an E34, but should be a similar process.
