MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
No. That way you would power Arduino Mega only.
When using 12V notebook PSU you can attach some female plug on RAMPS screw terminals and power up Arduino through it. That was my suggestion. Mind the polarity though.