The main problem with answering your question is that the manufacture is providing no technical information about the internal motor controller. Without that information it's hard to say if you can reverse the direction of rotation by say reversing the polarity of the battery or not. As to would a digital pot work, there is no information on the voltage or current level passing through the pot so again impossible to say without more information. My rule is to avoid buying assemblies like this unless proper datasheet information is avalible, otherwise you cannot be sure about a lot of things about it.
Perhaps if you contact the seller to see if more information is avalible or not?
Lefty