Do I need an appointment in Kalispell Mt, or is it first come first serve

No, they will do walk-ins but you will do better for an appointment. But getting an appointment will take some time...like 2-3 weeks out from the time you call to set it up. As a walk-in or with an appointment, you will register when you walk in and they will give you a number at the waiting area.

I came in on 5 dec and waited 42 minutes starting at noon.