For ghost ring sights, you will have to have the receiver drilled and tapped for the sight's screws.
On the front sight, you have two main options:
One is to have a GOOD gunsmith remove the old sight, then braze the rifle sight onto the barrel.
This requires a fair amount of skill to do it right, and requires refinishing the barrel, and usually polishing the bore.
Another option is to use one of the new clamp-on front sights.
These require only removing the front bead and attaching the new clamp sight.
Here's a link to Brownell's and the model they sell.
You can use both the sights, or use a different make rear with the clamp-on front:
http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=9203&title=TACTICAL+SHOTGUN+SIGHTS
Due to the ease of installation, the protective "ears" around the sight blade, and the strength, I think more and more people are going to be using this type of front sight.
To get the receiver drilled and tapped, you'll need to buy a rear sight first, then find a GOOD local gunsmith or machinist to drill and tap the receiver.
Be careful who you let do this, since I heard of several recent cases of people trusting someone, only to have the sight mounted off center.
This isn't rocket science, it's just a matter of good gunsmithing and paying attention.