Haz251, I really really like the Magpul gear. The stock is the most comfortable I have used, and is customizable for length and they sell cheek riser kits. I recommend getting the sling mount at the same time as it installs in place of one of the pieces they include with the stock. It is a huge improvement over the normal stock, and I much prefer it to the telescoping AR-style stocks (I don't really want a pistol grip on my shotgun). I highly recommend them.
As for your sights question, there are many sights that epoxy on top of the bead sight. The rear sight usually needs to be installed by a gunsmith, which is a permanent-type thing. I'd prefer a rail in the rear so I can swap out the site if I want, or put on an optic.
Since you mentioned wanting a rail and side saddle, I would look into Mesa Tactical's offerings. They have rails which are short for an optic, or full-length for standard AR-style BUISs. Then they can also include a side saddle. If you got the one pictured below, you would have your rail and side saddle covered in one stop, and could put on any sites you wanted.