Heres’s a solid introduction 3D printing from Incept 3D. | www.incept3D.com
Blender or other programs such as Inventor are used to make these models, to learn more about those programs and how to use them check this site out: http://3dprintingninja.blogspot.com.
Your computer does not need any internet access as you can model and print offline. As mentioned earlier most 3D printers print from an SD card so you can even turn your computer off while printing.