Haven't yet made the 3D printing dive. Open to recommendations though. I've eyed 3D printing for years. Is blender the open tool for designing here? Have yet to seriously get into that yet (sadly).
This coming year's new tech for me is raspberry pi with the kids. Last year's was FreeNAS (which is great).
I recommend dipping toes in at a local library, hackerspace, or community center (incl colleges and universities) They'll typically have intro classes worth checking out before deciding to buy a machine or not
There are many 3D model repos online with freely licensed content: YouMagine, Thingiverse, Pinshape, or search with Yeggi
To make your own 3D models, Blender, FreeCAD, OpenSCAD are the main FOSS options