If I upgrade to Facebook from a guest account will I keep my rank, coins, sticks?

Yes, all stats should remain the same, as connecting it to Facebook just adds any 8ball playing friends there to your Pool friends' list. You will be able to challenge them and send them gifts, and request gifts from them. You'll also be able to invite friends to play the game if they get the app (for a coin rewards). Doing this will, by default, set your 8Ball Pool profile picture to the one you are currently using on FB (I believe, though not sure if it will change your 8ball name- but that can be edited), which is easily changed by selecting an avatar you have in-game, and you can of course purchase a new avatar pic if you want to. I'm not sure if disconnecting Facebook will remove your FB friends, so be sure to jot down their unique IID if you do decide to disconnect the account. As far as I know this is accurate, but anyone feel free to correct me if I'm mistaken! Have fun.