Please check measurements against stock as from experience i have found some converters can change scale.
This was modeled in Fusion360 - NOT Sketchup
1. I have no idea of the polygon count etc
2. there should be a step file available - - i think its listed as 'other' .
3. I only modeled enough to be able to use this to produce 3d printed (sub 10 micron) parts from it (once chopped out of other geometry) - one of the pics is of some parts made in just this way ... i would say the model is 95% complete - - i may have missed what i considered 'inconsequential geometry' at the time ... but it worked perfectly for me - and all the printed parts were a nice snug fit.
DC - 3V - 6V 5V - 10MM Mini Coreless Motor Planetary Gear Reducer Motor for Robot