Question # 1: the air bags are triggered by the SRS module, no smashing of sensors or such, the SRS module is under your center console. Disconnecting the battery is always safe and wise.

Question #2: there is a guide rail for the back of the window that has been known to break and fall down in the bottom area of the inner door, the clunk you hear. There is a post at the below link that will tell you how to get the door panel off. (Replacing door latch) You might want to have the part when you go in there. The part number is car serial number specific or I'd tell you the part number.