Hi,
I did this with point and shoot camera, be sure to take some CHDK enabled canon camera.
Otherwhise each camera will choose it's own settings (ISO, aperture speed) but you need the same
settings for each pictures.
Also you can use CHDK to take picture via USB.
Since mine where not CHDK enabled my scans are not always good and I had to solder wire on the camera board :/
For alimentation you can get some nice DC/DC converter on ebay for 1$ each and use a computer 12V alimentation (those cost 15$ and you have a lot of power)
put the DC/DC converter close to the camera, the power loss in the cable is not negligeable (camera won't power up or will shut down during operation)