The basic question is: "Where do you want to insert some object?"
Is there any way to define this point? (Something like "in ratio to the objects center", "at a certain point hit by a ray casted from a certain point" or " centroid of some selection" - just to mention a few). If you know the way how to construct this point on the surface, you can construct a mm.Frame (origin + normal rotation) and transform the inserted object to that frame.
The basic workflow (here: based on a selection's centroid) is included in demo_08_transform_obj.py in the examples directory.
demo_02_spatialtest.py shows how to construct a mm.frame by hitting a ray against a surface (you want to know the "hitFrame").
Please provide more information about where you want to start...
