It might be a good idea to actually try one out before you buy it, I always found scope and sights beyond beads or a simple notch and blad to be useless on shotguns. I might change my mind if I had a rifled slug barrel.
FuryFour: The Mossberg 500 I own [model 50577] has a bead front sight and is drilled/tapped for a rear sight. Do I need
a gunsmith to install the trueglow sights you recommended?
if you're using it for birds, clays and HD, not turkeys, I would leave it alone...for dynamic targets, you need to be looking at the target, not the sights...
If your bead is the metal type, I would tell you to paint it a flourescent color of your choice and leave it alone. Let me tell you why. I've got a Mossberg 835 which comes with a plastic front sight. Mine didn't last very long before it broke off. Doing some research, I found that this is a VERY common thing. So much so that I'd gladly screw in a brass bead if I had one.
FuryFour: The Mossberg 500 I own [model 50577] has a bead front sight and is drilled/tapped for a rear sight. Do I need
a gunsmith to install the trueglow sights you recommended?
No, the truglow sights I mention just snap on. On my win 1300 it snapped onto the barrel and on my 870 (ribbed) it snapped onto the rib and used a magnet to stay in place. Both are very sturdy and will not move on their own