Thanks for the post and excellent pictures. Unlike all of the other people in the threads I was unable to complete the task and had to drive 2 ½ hours to the dealer for completion. My car is a 2002 530i. I was able to remove the side panel and panel below glove box. Also unplugged connector from the FSU and loosened the FSU from the receptacle by pushing on the retaining clasp. I could move the FSU 4-5 mm but it hung up on surrounding ducts and blower parts. I moved it in all directions but with no success.
The technician at the BMW dealer was able to remove it in seconds. He stated I needed to push the FSU up (toward the sky) and then rotate it slightly to allow it to come out. No further parts were removed by him.
He then told me that no diagnostics were necessary as almost all fan problems are related to the FSU. They charged me for the part and 20 minutes of labor. (seemed honest and fair).
I hope this can help some of you if you also have trouble getting the FSU free of surrounding structures.