Yeah, to get to the two nuts on top (don't remove the center top mount nut) you need to remove the side bolsters (one 10mm bolt under the bottom between the bolster and the seat bottom. Then lay the seat back forward, remove the plastic tray on top, then you should have access.

Once you remove those nuts, the spring/shock assembly should be loose, but like you said, it probably won't quite fall out. You will probably have to have someone else come out and stand on the rear rotor/drum to push the spindle down to give you more room. You should eventually be able to fenagle it out.