When I read your post, it sound like you are trying to replace the air filter by removing the entire air filter box. LOL

I haven't changed the air filter in the X5 myself yet, but for all the other BMWs I own, you just unclip the the clips and open the top cover and replace the filters. No tools needed (maybe a flat head screw driver if your hand can't reach some of the clips)

The top cover doesn't come completely off, it flexes a bit, just enough to get the old filter out and put a new filter in.