The belts are tooth down, and rarely, if ever become dirty --- if they do they are easily cleaned (or replaced if need be).
Assembling the machine is a good way to get to know the machine and its mechanisms for troubleshooting and maintenance.
The base Shapeoko includes everything one needs save for a computer and Internet connection (to download software, and I've burned CDs for folks who didn't have Internet):
- software (which runs locally, no network access needed save to update)
- CNC machine
- tools for assembly
- endmill
- dust shoe
with the option of bundling a trim router or using your own.
Accessories* are just that, optional add-ons which some folks want, but many folks do without --- when one does add them all, one gets a very nice synergy enabled by the fact that we write our own software. Interestingly, that includes MeshCAM which is developed by one of the partners at Carbide 3D.
* accessories include BitZero (a corner probe), BitSetter (a tool length offset measurer), BitRunner (a relay to turn the spindle on/off --- mine also does my vacuum), and the HDZ (an optional Z-axis which affords the greater precision of a ballscrew, and a narrower and taller carriage which affords more travel along X and Z), as well as a full line of workholding options.