Are you trying to install diferent speakers or something else. The stock speaker grilles will pop out with a small flat bladed tool. I used a thin putty knife. I wouldn't mess with the headrests. You have to approach them from the trunk. They can be removed, but, unless you are leaving them out, I wouldn't touch them. If you really are pursuing a different speaker setup, check with a local automotive stereo shop and see what they have to offer. So often when we try to accomplish a seemingly simple modification, we get ourselves into trouble with other assorted mechanical devices and the original job then pales to insignificance. Good luck...
1987 BMW 325