I don't have a 500 to take pictures of, but I do have an 870. Here are the locations of the safety and the action release:
On Mossberg 500s and 590s, the safety is located on the tang of the receiver (on the top near where the stock is attached to the receiver) and the action release is located behind the trigger guard on the left side, and is smaller and more rounded.
And before anyone gets on my case, the serial number is photoshopped out for security reasons.
Not a great image but need to locate digi batts to charge up for better...
The safety is quite visible on top of receiver. You can barely see the action release on left side of rear end of trigger guard. As you can see it protrudes rearward just enuff so your right hand middle finger can easily operate it while gun is in full mount without the need to take either hand from your favorite position or location on the gun.
Brent