Do I need to schedule an appointment to have my cracked screen iPhone fixed or can I just walk in to the store and ask them instead?

Do I need to schedule an appointment to have my cracked screen iPhone fixed or can I just walk in to the store and ask them instead?

No

Just live with the cracked screen. You, or someone else, will inadvertently end up cracking the screen again. Get yourself a shock-proof case if you wish.

Depends on how busy that particular Apple store is. If the techs working there in the back are not super busy, they may just take a few minutes and take care of it while you wait, but don't hold your breath or throw a fit if they can't. You can always call ahead to see if they are busy.