Most scanners manufactured today use what is called a CIS assembly ( contact image sensor ).
Most times a lamp or LED is used to illuminate the documnet and then the CIS assembly is moved accross the document at a speed depending on the resolution desired. Most of these are serial in nature but some high speed / high resolution scanners are parallel.
Some scanners are twain compliant sending the information while others rely on software from the host PC to render the image.
Controlling the motors should not be too bad. They are mostly fine steppers. controlling the CIS part of it I am not sure of. I have looked at data sheets from a couple mounted in copiers just out of curiosity but never really examined what they do or how they do it via software.
Most micro fische type scanners I have seen work in a simular fashion. They place a bright led/lamp behind the fishe and replect it off a white plate for scanning via the CIS/CCD unit. Most of these I have seen are CCD based for micro fische. I do not work on "Film" scanners but I assume they work in a simular fashion to the two I mentioned.
Hope this helps.