I have used the pass this week at magic kingdom as Hollywood studios. Magic kingdom in my opinion is useless. I will never drive to that park again! Hollywood studios was awesome. First row. Parking not far from the bus drop off.
Varies by AAA location. At mine you have to book the package. Others have reported getting it just for buying tickets
Rememeber you still have to pay for parking if you are not on site. Plus if the AAA spaces are full or in use you won't get anything. For example, the Epcot spots are often taken by race set ups. (marathon, food and wine marathon etc...)
Just to make sure you're clear, the AAA Diamond Parking Pass doesn't exempt you from having to pay to park at Disney (if you're staying at an onsite resort, it's a moot point). The people at the booths can direct you to follow the blue line to the AAA lot (which is typically next to the handicap spaces).