I don't know Modo, and I won't answer to your main questions, but.
For the objects:
- ArchiCAD can import SketchUp models pretty well.
- There are lots of ArchiCAD Objects on the internet, for free (BIMcomponents.com and some others, take a look)
Object Making with ArchiCAD
- Try the MORPH tool, It's a lot like SketchUp
- If you have the time, you might want to start learning GDL (Geometrics Description Language), the basic language used by ArchiCAD for making objects.
hope you'll find what you need, or find the proper tools to do what you want to do!
Cheers
