I have a 2007 Sprinter Great West Vans. The Fiamma awning on it is also attached with three brackets. To access the awning attachment screws I need to open the awning a few feet. There are 2 or 3 screws that go through the back of the awning case and into each bracket. Yours may be attached in the same or similar manner. Good luck.
My Fiamma has 3 brackets, the awning is attached with 2 pop rivets on the bottom of the front and rear brackets, none in the middle. No need to open awning.