It's really not too hard, just kind of working in the dark. The end inside the roof is a ball and socket design. You just have to pry the strut up to get it off. Here's a link to Bill R.'s excellent service manual procedure, and a reply from me about not really needing the 'special tool'.
http://www.bimmer.info/forum/showthr...r+glass+struts
Here's another post from Roadfly:
http://bimmer.roadfly.com/bmw/forums/e34/5561624-1.html
The instructions I used were on the old board format, and I can't get a search to work for it.
Once you loosen things up, you basically just take off the snap ring retainer thing that you can see. Then you have to stick a very long 14" screwdriver thing back in the roof to pry up the socket end of the strut up off the ball. There's a rubber grommet that you have to stick the screwdriver thru to get back to the ball. Putting the new one on is just the reverse, knowing when the ball engages the socket was a little bit difficult. Make sure you have something like a long 2x4 to prop up the glass while you're working on it.
Good luck, if you get stumped give me a holler. Perhaps one of the most satisfying fixes I've done, although I may have permanent brain damage from the damn thing dropping on me.