Acoustic guitar saddle questions.

It is very, very, very, very rare that you will buy a nut or a saddle that are stick-on ready. Saddles are typically too tall, too thick, too thin, etc., and will have to be finely modified to fit your guitar, set action right and stuff. So don't be discouraged if you get a replacement saddle and it's not perfect straight out of the gate. They NEVER are, for all practical purposes.

I have yet to find a saddle material (or nut material for that matter) that I like as much as bone. Just get bone.

Usually saddles are not glued into the bridge. If the old one is difficult to remove, it's more likely due to a tight saddle slot. Pull straight up with pinch nose pliers if it's stuck.

Use the old one as the gauge as to how much material you need to take off the new one and where. Use adhesive sandpaper stuck to a tabletop to remove material. That will help to keep things straight and square.

Take off a little at a time, check your progress and then take off a little more. The golden rule is you can always take off a little more but putting material back is a bit more challenging.

It goes without saying make sure your guitar's other set-up points (truss rod/relief, nut slots) are dialed in before you replace the saddle.

Edited to add advice from a guy who does this for a living to a guy who rarely if ever does this ... get two saddles, maybe even three when you buy your blanks. I can almost promise you if you have never done this before, that the first one will end up somewhere between rendered useless and destroyed when you are done with it. But it will teach you what to do and what not to do when you begin work on that second saddle.

Not at all unheard of, put an non-compensated saddle on first. Like we said above, saddles are cheap. If intonation is very negatively affected (I don't think it will be), go back to a compensated saddle. You gleaned practice seating that first saddle, the second will likely fit a little better!