I'll make a couple of assumptions.. one is that you have a rail, that it can be driven by the motor physically (geared to it, screw drive, what have you, as long as rotation of the motor causes the camera to travel), that kind of thing.
Since it seems like you are just getting started, I'd skip soldering boards, and like these guys are suggesting, get a stepper controller "shield". There are a number of them, I'm a fan of Adafruit and Rugged Circuits, but they are typically fairly similar.. They are just a series of digital switches which can handle the actual load of a motor, which an Arduino can't directly. Happily, these are not all that particular about voltage or current requirements of most small to midsized steppers, within reason.. they can usually handle most DC steppers other than heavy CNC stuff. Your stepper motor will list it's requirements in terms of voltage and current, you are just going to get a controller board capable of that or greater. As for the arduino, any of them is fine for the project, so I'd just get an Uno to keep it all simple as possible.
You are also going to want an optocoupler, I use 4n25 and pc817, but basically any NPN optocoupler will do, and a resistor for it, 1k ohm or so. This acts as a way to electrically protect the camera while allowing the arduino to operate the shutter via a cable release port (2.5mm on most SLR's).
From there, it's a matter of working out how the bits go together, and taking a whack at working out how to do it in code. Rest assured, you are not facing a huge coding effort... but I'll suggest that you take some time, and learn a bit about the whole thing. Arduino is a heck of a powerful tool for photography.
I'm currently building a 10K lumen LED photo special effects flash with Arduino control at it's core.
Read, do some browsing, particularly around the "Playground" areas, and search the forums for some similar stuff. It's here to be found. If you do actually get stuck-- the folks here are more than happy to help.. the general requirement is one of "Sure we'll help, but you need to try it yourself first." - but in a good way.