Replacing the Mossberg 500 safety is not a difficult task and can usually be accomplished in 10-15 minutes

Tools needed:

Flat head screw driver

Masking tape (optional)

1.  The first step is to open the action and make sure that the safety is in the safe position.  We will leave the action open for the remainder of this procedure.  Opening the action and putting the safety on "safe" prevents safety components from falling into the receiver.  

2.  Second, you may apply masking tape on the receiver around the safety.  Masking tape can help prevent scratches on the receiver should your screw driver slip while removing the stock safety screw and it has the benefit of leaving little to no residue behind after removal.  If you're going to go this route, it is reccomended to apply two layers of tape.  

3. Now it's time to remove the safety.  It should be noted that underneath the safety switch there is a small ball bearing sitting on top of a spring and a thin metal plate (figure 1).  These components are needed to install the new safety, so use caution so as not to lose them.  The factory safety uses a tamper proof screw that is only designed to be tightened.  The key to removing the tamper proof screw is to bear down on it with a screw driver that has nice sharp corners.  

Mossberg safety internal components

Figure 1: These parts are under the safety.  Don't lose them! 

Removing mossberg safety

Figrue 2: Removing the factory safety.  Note that the action is open and the safety is all the way back in the "safe" position.  

4. Once the factory safety is removed, we can start installing the new one.  The Triceratops Customs Enhanced Mossberg Safeties are reversible to accomodate a variety of hand sizes and prefrences.  This means that they can be installed with either the steeper ramp facing the user or the shallower ramp.  You may choose either direction, just make sure that the holes in the metal plate line up with the detents in the safety for the direction you choose (Figure 3 and 4).    Ensure that the ball bearing and spring are in their proper place and install the safety with the included cap screw and hex wrench (Figure 5).

Figure 3: Standard configuration.  Note the direction that the metal plate lines up to the holes of the safety.  Make sure to install the safety so that the ball bearing can rest inside these detents.

Figure 4: This is the "reverse" installation.  This may be more comfortable for users with smaller hands or with the use of certain pistol grip stocks.  Again, note the direction of the plate relative to the safety.

Figure 5: Ready to install the new safety with the ball bearing positioned on the spring.

Once assembled, test the safety actuation to ensure that everything went together correctly.