I have done this job on an e30 ('84 318i) so I can tell you that it can be
done.  I do recall that it took many attempts to get things oriented just
right so that the assembly would come out and that I went back to the book
several times to make sure I wasn't missing something because it seemed as
though it was impossible.  Also I recall that even after finding the best
orientation that there was some interference between the left hand wiper
shaft and the sheet metal of the heater plenum.  Not enough interference
that anything got permanently bent but enough that the upper wall of the
plenum had to be sprung out of the way.  Just keep trying.